import sys
import numpy as np

m = 10**9+7

def syuke(n,r):
    ue=1
    sit=1
    r =min(r,n-r)
    for i in range(r):
        ue = (ue*(n-i))%m
        sit = (sit*(i+1))%m
    return(ue*pow(sit,(m-2),m))

n,a,b = map(int,input().split())

syu = 0
if n<3:
    print(0)
    sys.exit()
syu = pow(2,n,m)-1
syu -= syuke(n,a)%m
syu -= syuke(n,b)%m
print(syu%m) import sys sys import numpy as np numpy m = 10**9+7 m 10**9+7 10**9 10 9 7 def syuke(n,r):
    ue=1
    sit=1
    r =min(r,n-r)
    for i in range(r):
        ue = (ue*(n-i))%m
        sit = (sit*(i+1))%m
    return(ue*pow(sit,(m-2),m)) syuke ue=1 ue 1 sit=1 sit 1 r =min(r,n-r) r min(r,n-r) min r n-r n r for i in range(r):
        ue = (ue*(n-i))%m
        sit = (sit*(i+1))%m
     i range(r) range r ue = (ue*(n-i))%m ue (ue*(n-i))%m ue*(n-i) ue n-i n i m sit = (sit*(i+1))%m sit (sit*(i+1))%m sit*(i+1) sit i+1 i 1 m return(ue*pow(sit,(m-2),m)) ue*pow(sit,(m-2),m) ue pow(sit,(m-2),m) pow sit m-2 m 2 m n n r r n,a,b = map(int,input().split()) n map(int,input().split()) map int input().split() ().split () input split a b syu = 0 syu 0 if n<3:
    print(0)
    sys.exit() n<3 n 3 print(0) print 0 sys.exit() sys.exit sys exit syu = pow(2,n,m)-1 syu pow(2,n,m)-1 pow(2,n,m) pow 2 n m 1 syu -= syuke(n,a)%m syu syuke(n,a)%m syuke(n,a) syuke n a m syu -= syuke(n,b)%m syu syuke(n,b)%m syuke(n,b) syuke n b m print(syu%m) print syu%m syu m n,a,b = map(int,input().split()) map(int,input().split()) n syu = pow(2,n,m)-1 pow(2,n,m)-1 syu syu -= syuke(n,b)%m syuke(n,b)%m syu a,b = map(int,input().split()) map(int,input().split()) a def syuke(n,r):
    ue=1
    sit=1
    r =min(r,n-r)
    for i in range(r):
        ue = (ue*(n-i))%m
        sit = (sit*(i+1))%m
    return(ue*pow(sit,(m-2),m)) def syuke(n,r):
    ue=1
    sit=1
    r =min(r,n-r)
    for i in range(r):
        ue = (ue*(n-i))%m
        sit = (sit*(i+1))%m
    return(ue*pow(sit,(m-2),m)) syuke syu = 0 0 syu b = map(int,input().split()) map(int,input().split()) b syu -= syuke(n,a)%m syuke(n,a)%m syu m = 10**9+7 10**9+7 m
import sys
import numpy as np

m = 10**9+7

def syuke(n,r):
    ue=1
    sit=1
    r =min(r,n-r)
    for i in range(r):
        ue = (ue*(n-i))%m
        sit = (sit*(i+1))%m
    return(ue*pow(sit,(m-2),m))

n,a,b = map(int,input().split())

syu = 0
if n<3:
    print(0)
    sys.exit()
syu = pow(2,n,m)-1
syu -= syuke(n,a)%m
syu -= syuke(n,b)%m
print(syu%m)