#include <iostream>

typedef long long ll;

const ll MOD = 1000000007;

ll mult(ll a, ll b){ 
   if(b==0) return 1;

   ll g = mult(a, b/2); 
   if(b%2) return g * g % MOD * a % MOD;
   return g * g % MOD;
}

ll C(ll n, ll k){ 
   if(k>n || k<0) return 0;
   ll gt = 1;
   ll rev = 1;
   for(int i=n; i>=n-k+1; --i) gt = (gt*i) % MOD;
   for(int i=1; i<=k; ++i) rev = (rev*i) % MOD;

   return gt * mult(rev, MOD-2) % MOD;
}

int main(){
   ll n, a, b;
   std::cin >> n >> a >> b;

   std::cout << ((mult(2, n) - C(n, a) - C(n, b) - 1 + MOD)%MOD + MOD)%MOD << std::endl;
   return 0;
}
