#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9 + 7;
ll qpow(ll a, ll b)
{
    ll r = 1;
    for (;b;b>>=1,a=a*a%MOD)
        if (b&1)
            r = r*a%MOD;
    return r;
}
ll c(ll n, ll k)
{
    ll u = 1, d = 1;
    for (int i = 0; i < k; ++i) {
        u = u * (n - i) % MOD;
        d = d * (i + 1) % MOD;
    }
    return u * qpow(d, MOD - 2) % MOD;
}
int main()
{
    ll n,a,b;
    cin >> n >> a >> b;
    ll ans = qpow(2, n) + MOD - 1 + MOD - c(n, a) + MOD - c(n, b);
    cout << ans % MOD << endl;
}
