#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0), cin.tie(NULL), cout.tie(NULL);     int a, b, c;     cin >> a >> b >> c;     cout << ((a + c - 1) * (b + c - 1) - c * (c - 1)) <<   n ;     return 0;   }   