def main():
    H, W = (int(_) for _ in input().split())
    S = [input() for _ in range(H)]
    yoko = [[0] * W for _ in range(H)]
    tate = [[0] * W for _ in range(H)]

    for i in range(H):
        right = 0
        cc = 0
        for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
    for i in range(W):
        bottom = 0
        cc = 0
        for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
    output = 0
    for i in range(H):
        for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
    print(output)
    return

if __name__ == '__main__':
    main() def main():
    H, W = (int(_) for _ in input().split())
    S = [input() for _ in range(H)]
    yoko = [[0] * W for _ in range(H)]
    tate = [[0] * W for _ in range(H)]

    for i in range(H):
        right = 0
        cc = 0
        for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
    for i in range(W):
        bottom = 0
        cc = 0
        for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
    output = 0
    for i in range(H):
        for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
    print(output)
    return main int(_) for _ in input().split() for _ in input().split() _ input().split() ().split () input split for _ in input().split() int(_) int _ H, W = (int(_) for _ in input().split()) H (int(_) for _ in input().split()) W input() for _ in range(H) for _ in range(H) _ range(H) range H for _ in range(H) input() input S = [input() for _ in range(H)] S [input() for _ in range(H)] [0] * W for _ in range(H) for _ in range(H) _ range(H) range H for _ in range(H) [0] * W [0] 0 W yoko = [[0] * W for _ in range(H)] yoko [[0] * W for _ in range(H)] [0] * W for _ in range(H) for _ in range(H) _ range(H) range H for _ in range(H) [0] * W [0] 0 W tate = [[0] * W for _ in range(H)] tate [[0] * W for _ in range(H)] for i in range(H):
        right = 0
        cc = 0
        for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
     i range(H) range H right = 0 right 0 cc = 0 cc 0 for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
     left range(W) range W if S[i][left] == '#':
                cc = 0
                right += 1
                continue
             S[i][left] == '#' S[i][left] [i] S i left '#' cc = 0 cc 0 right += 1 right 1 continue while right < W and S[i][right] == '.':
                right += 1
             right < W and S[i][right] == '.' right < W right W S[i][right] == '.' S[i][right] [i] S i right '.' right += 1 right 1 cc = right - left cc right - left right left if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
     left > 0 and S[i][left-1] == '.' left > 0 left 0 S[i][left-1] == '.' S[i][left-1] [i] S i left-1 left 1 '.' for i in range(W):
        bottom = 0
        cc = 0
        for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
     i range(W) range W bottom = 0 bottom 0 cc = 0 cc 0 for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
     top range(H) range H if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
             S[top][i] == '#' S[top][i] [top] S top i '#' cc = 0 cc 0 bottom += 1 bottom 1 continue while bottom < H and S[bottom][i] == '.':
                bottom += 1
             bottom < H and S[bottom][i] == '.' bottom < H bottom H S[bottom][i] == '.' S[bottom][i] [bottom] S bottom i '.' bottom += 1 bottom 1 cc = bottom - top cc bottom - top bottom top if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
     top > 0 and S[top-1][i] == '.' top > 0 top 0 S[top-1][i] == '.' S[top-1][i] [top-1] S top-1 top 1 i '.' output = 0 output 0 for i in range(H):
        for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
     i range(H) range H for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
     j range(W) range W output = max(output, yoko[i][j]+tate[i][j]-1) output max(output, yoko[i][j]+tate[i][j]-1) max output yoko[i][j]+tate[i][j]-1 yoko[i][j]+tate[i][j] yoko[i][j] [i] yoko i j tate[i][j] [i] tate i j 1 print(output) print output return if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    H, W = (int(_) for _ in input().split())
    S = [input() for _ in range(H)]
    yoko = [[0] * W for _ in range(H)]
    tate = [[0] * W for _ in range(H)]

    for i in range(H):
        right = 0
        cc = 0
        for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
    for i in range(W):
        bottom = 0
        cc = 0
        for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
    output = 0
    for i in range(H):
        for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
    print(output)
    return def main():
    H, W = (int(_) for _ in input().split())
    S = [input() for _ in range(H)]
    yoko = [[0] * W for _ in range(H)]
    tate = [[0] * W for _ in range(H)]

    for i in range(H):
        right = 0
        cc = 0
        for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
    for i in range(W):
        bottom = 0
        cc = 0
        for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
    output = 0
    for i in range(H):
        for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
    print(output)
    return main
def main():
    H, W = (int(_) for _ in input().split())
    S = [input() for _ in range(H)]
    yoko = [[0] * W for _ in range(H)]
    tate = [[0] * W for _ in range(H)]

    for i in range(H):
        right = 0
        cc = 0
        for left in range(W):
            if S[i][left] == '#':
                cc = 0
                right += 1
                continue
            while right < W and S[i][right] == '.':
                right += 1
            cc = right - left
            if left > 0 and S[i][left-1] == '.': yoko[i][left] = yoko[i][left-1]
            else: yoko[i][left] = cc
    for i in range(W):
        bottom = 0
        cc = 0
        for top in range(H):
            if S[top][i] == '#':
                cc = 0
                bottom += 1
                continue
            while bottom < H and S[bottom][i] == '.':
                bottom += 1
            cc = bottom - top
            if top > 0 and S[top-1][i] == '.': tate[top][i] = tate[top-1][i]
            else: tate[top][i] = cc
    output = 0
    for i in range(H):
        for j in range(W):
            output = max(output, yoko[i][j]+tate[i][j]-1)
    print(output)
    return

if __name__ == '__main__':
    main()
