#include <bits/stdc++.h>
#pragma comment(linker, "/stack:336777216")
#pragma GCC optimize("O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
ll const mod = 1000000007;
ll n, k, s, m;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(nullptr);
  ll a, b, c;
  cin >> a >> b >> c;
  cout << (a * b * c) - (a - 1) * (b - 1) * (c - 1) << '\n';
  return 0;
}
