### BUGGY CODE ###

import sys
sys.setrecursionlimit(10**6)
from math import floor,ceil,sqrt,factorial,log
from heapq import heappop, heappush, heappushpop
from collections import Counter,defaultdict,deque
from itertools import accumulate,permutations,combinations,product,combinations_with_replacement
from bisect import bisect_left,bisect_right
from copy import deepcopy
from operator import itemgetter
from fractions import gcd
mod = 10 ** 9 + 7
inf = float('inf')
ninf = -float('inf')
 
#整数input
def ii(): return int(sys.stdin.readline().rstrip()) #int(input())
def mii(): return map(int,sys.stdin.readline().rstrip().split())
def limii(): return list(mii()) #list(map(int,input().split()))
def lin(n:int): return [ii() for _ in range(n)]
def llint(n: int): return [limii() for _ in range(n)]
#文字列input
def ss(): return sys.stdin.readline().rstrip() #input()
def mss(): return sys.stdin.readline().rstrip().split()
def limss(): return list(mss()) #list(input().split())
def lst(n:int): return [ss() for _ in range(n)]
def llstr(n: int): return [limss() for _ in range(n)]

#本当に貪欲法か？ DP法では？？
#本当に貪欲法か？ DP法では？？
#本当に貪欲法か？ DP法では？？

n,a,b=mii()

if n==2 and a==1 and b==2:
    print(0)
    exit()

#ncrの場合
# nCr % mod と同等
N=100
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル
#テーブル作成
for j in range( 2, N + 1 ):
    g1.append( ( g1[-1] * j ) % mod )
    inverse.append( ( -inverse[mod % j] * (mod//j) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )
#nCrとmodを入力
def cmb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod
def p_f(a,n,p):
    bi=str(format(n,"b"))#2進表現に
    res=1
    for i in range(len(bi)):
        res=(res*res) %p
        if bi[i]=="1":
            res=(res*a) %p
    return res
def mod_combination(n, k, mod):
    # nCk (mod m)
    def mod_permutation(n, k, mod):
        if n<=k:
            return 1
        else:
            return (n * mod_permutation(n-1,k,mod))%mod

    def mod_inv_permutation(k, mod):
        k, mod = int(k), int(mod)
        if k<=1:
            return 1
        else:
            return (pow(k,mod-2,mod) * mod_inv_permutation(k-1, mod))%mod

    return (mod_permutation(n,n-k,mod) * mod_inv_permutation(k, mod))%mod

ans=(p_f(2,n,mod) -1)%mod -mod_combination(n,a,mod)%mod - mod_combination(n,b,mod)%mod
print(ans%mod) 

### FIXED CODE ###

import sys
sys.setrecursionlimit(10**6)
from math import floor,ceil,sqrt,factorial,log
from heapq import heappop, heappush, heappushpop
from collections import Counter,defaultdict,deque
from itertools import accumulate,permutations,combinations,product,combinations_with_replacement
from bisect import bisect_left,bisect_right
from copy import deepcopy
from operator import itemgetter
from fractions import gcd
mod = 10 ** 9 + 7
inf = float('inf')
ninf = -float('inf')
 
#整数input
def ii(): return int(sys.stdin.readline().rstrip()) #int(input())
def mii(): return map(int,sys.stdin.readline().rstrip().split())
def limii(): return list(mii()) #list(map(int,input().split()))
def lin(n:int): return [ii() for _ in range(n)]
def llint(n: int): return [limii() for _ in range(n)]
#文字列input
def ss(): return sys.stdin.readline().rstrip() #input()
def mss(): return sys.stdin.readline().rstrip().split()
def limss(): return list(mss()) #list(input().split())
def lst(n:int): return [ss() for _ in range(n)]
def llstr(n: int): return [limss() for _ in range(n)]

#本当に貪欲法か？ DP法では？？
#本当に貪欲法か？ DP法では？？
#本当に貪欲法か？ DP法では？？

n,a,b=mii()

if n==2 and a==1 and b==2:
    print(0)
    exit()


def p_f(a,n,p):
    bi=str(format(n,"b"))#2進表現に
    res=1
    for i in range(len(bi)):
        res=(res*res) %p
        if bi[i]=="1":
            res=(res*a) %p
    return res
def nCk(n, k, mod=10 ** 9 + 7):
    if n < k:
        return 0
    k = min(k, n - k)
    numer = 1
    for x in range(n - k + 1, n + 1):
        numer = (numer * x) % mod
    denom = 1
    for x in range(1, k + 1):
        denom = (denom * x) % mod
    return numer * pow(denom, mod - 2, mod) % mod
 

ans=(p_f(2,n,mod) -1)%mod -nCk(n,a,mod)%mod - nCk(n,b,mod)%mod
print(ans%mod)