#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[3];
  scanf("%d %d %d", &a[0], &a[1], &a[2]);
  sort(a, a + 3);
  int t = a[0] - 1;
  printf("%d\n", (a[1] + t) * (a[2] + t) - t * (t + 1));
}
