#include <iostream>
using namespace std;

using ll = long long;
ll mod = 1e9 + 7;

ll power(ll n, ll p){   // n^p % mod    
    if(p == 0) return 1;
    if(p % 2 == 0){
        ll half = power(n, p/2);
        return half * half % mod;
    }else{
        return n * power(n, p-1) % mod;
    }
}

ll comb(ll n, ll k){
    ll ans = 1;
    for(int i=1; i<=k; i++){
        ans = ((ans * (n-i+1)) % mod * power(i, mod-2) % mod ) % mod;
    }
    return ans;
}

int main()
{
    ll n, a, b;
    cin >> n >> a >> b;
    ll ans = power(2, n) - comb(n, a) - comb(n, b) -1;
    while(ans < 0) ans += mod;
    cout << ans << endl;
    return 0;
}
