#include <bits/stdc++.h>
using namespace std;
long long n,a,b;
long long dfs(long long n,long long m){
    long long cnt=1;
    for(long long i=1;i<=m;i++){
       	cnt*=n-i+1;
        cnt/=i;
    }
    return cnt;
}
signed main(){
    cin>>n>>a>>b;
    long long tmp1=dfs(a+n,n),tmp2=dfs(b+n,n);
   	cout<<tmp1*tmp2;
    return 0;
}