#include <bits/stdc++.h>
int main() {
  std::vector<int> xs(3);
  for (int& x : xs) std::cin >> x;
  std::sort(xs.begin(), xs.end());
  std::cout << (xs[0] - 1) * (xs[1] + xs[2] - 1) + xs[1] * xs[2] << '\n';
}
