def main():
    H, W = map(int, input().split())
    S = []
    for _ in range(H):
        s = list(input())
        S.append(s)
    R = [[0]*W for _ in range(H)]
    L = [[0]*W for _ in range(H)]
    U = [[0]*W for _ in range(H)]
    D = [[0]*W for _ in range(H)]
    for i in range(H):
        cnt1 = 0
        cnt2 = 0
        for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
        for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

    for j in range(W):
        cnt1 = 0
        cnt2 = 0
        for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
        for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

    ans = 0
    for i in range(H):
        for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
    print(ans)


if __name__ == '__main__':
    main() def main():
    H, W = map(int, input().split())
    S = []
    for _ in range(H):
        s = list(input())
        S.append(s)
    R = [[0]*W for _ in range(H)]
    L = [[0]*W for _ in range(H)]
    U = [[0]*W for _ in range(H)]
    D = [[0]*W for _ in range(H)]
    for i in range(H):
        cnt1 = 0
        cnt2 = 0
        for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
        for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

    for j in range(W):
        cnt1 = 0
        cnt2 = 0
        for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
        for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

    ans = 0
    for i in range(H):
        for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
    print(ans) main H, W = map(int, input().split()) H map(int, input().split()) map int input().split() ().split () input split W S = [] S [] for _ in range(H):
        s = list(input())
        S.append(s)
     _ range(H) range H s = list(input()) s list(input()) list input() input S.append(s) S.append S append s [0]*W for _ in range(H) for _ in range(H) _ range(H) range H for _ in range(H) [0]*W [0] 0 W R = [[0]*W for _ in range(H)] R [[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 L = [[0]*W for _ in range(H)] L [[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 U = [[0]*W for _ in range(H)] U [[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 D = [[0]*W for _ in range(H)] D [[0]*W for _ in range(H)] for i in range(H):
        cnt1 = 0
        cnt2 = 0
        for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
        for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

     i range(H) range H cnt1 = 0 cnt1 0 cnt2 = 0 cnt2 0 for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
         j range(W) range W if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
         S[i][j]=='#' S[i][j] [i] S i j '#' cnt1 = 0 cnt1 0 cnt1 += 1 cnt1 1 L[i][j] = cnt1 L[i][j] [i] L i j cnt1 for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

     j range(W-1, -1, -1) range W-1 W 1 -1 -1 if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

     S[i][j]=='#' S[i][j] [i] S i j '#' cnt2 = 0 cnt2 0 cnt2 += 1 cnt2 1 R[i][j] = cnt2 R[i][j] [i] R i j cnt2 for j in range(W):
        cnt1 = 0
        cnt2 = 0
        for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
        for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

     j range(W) range W cnt1 = 0 cnt1 0 cnt2 = 0 cnt2 0 for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
         i range(H) range H if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
         S[i][j]=='#' S[i][j] [i] S i j '#' cnt1 = 0 cnt1 0 cnt1 += 1 cnt1 1 U[i][j] = cnt1 U[i][j] [i] U i j cnt1 for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

     i range(H-1,-1,-1) range H-1 H 1 -1 -1 if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

     S[i][j]=='#' S[i][j] [i] S i j '#' cnt2 = 0 cnt2 0 cnt2 += 1 cnt2 1 D[i][j] = cnt2 D[i][j] [i] D i j cnt2 ans = 0 ans 0 for i in range(H):
        for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
     i range(H) range H for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
     j range(W) range W ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3) ans max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3) max ans L[i][j]+R[i][j]+U[i][j]+D[i][j]-3 L[i][j]+R[i][j]+U[i][j]+D[i][j] L[i][j]+R[i][j]+U[i][j] L[i][j]+R[i][j] L[i][j] [i] L i j R[i][j] [i] R i j U[i][j] [i] U i j D[i][j] [i] D i j 3 print(ans) print ans if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    H, W = map(int, input().split())
    S = []
    for _ in range(H):
        s = list(input())
        S.append(s)
    R = [[0]*W for _ in range(H)]
    L = [[0]*W for _ in range(H)]
    U = [[0]*W for _ in range(H)]
    D = [[0]*W for _ in range(H)]
    for i in range(H):
        cnt1 = 0
        cnt2 = 0
        for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
        for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

    for j in range(W):
        cnt1 = 0
        cnt2 = 0
        for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
        for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

    ans = 0
    for i in range(H):
        for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
    print(ans) def main():
    H, W = map(int, input().split())
    S = []
    for _ in range(H):
        s = list(input())
        S.append(s)
    R = [[0]*W for _ in range(H)]
    L = [[0]*W for _ in range(H)]
    U = [[0]*W for _ in range(H)]
    D = [[0]*W for _ in range(H)]
    for i in range(H):
        cnt1 = 0
        cnt2 = 0
        for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
        for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

    for j in range(W):
        cnt1 = 0
        cnt2 = 0
        for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
        for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

    ans = 0
    for i in range(H):
        for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
    print(ans) main
def main():
    H, W = map(int, input().split())
    S = []
    for _ in range(H):
        s = list(input())
        S.append(s)
    R = [[0]*W for _ in range(H)]
    L = [[0]*W for _ in range(H)]
    U = [[0]*W for _ in range(H)]
    D = [[0]*W for _ in range(H)]
    for i in range(H):
        cnt1 = 0
        cnt2 = 0
        for j in range(W):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                L[i][j] = cnt1
        for j in range(W-1, -1, -1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                R[i][j] = cnt2

    for j in range(W):
        cnt1 = 0
        cnt2 = 0
        for i in range(H):
            if S[i][j]=='#':
                cnt1 = 0
            else:
                cnt1 += 1
                U[i][j] = cnt1
        for i in range(H-1,-1,-1):
            if S[i][j]=='#':
                cnt2 = 0
            else:
                cnt2 += 1
                D[i][j] = cnt2

    ans = 0
    for i in range(H):
        for j in range(W):
            ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)
    print(ans)


if __name__ == '__main__':
    main()