#include <bits/stdc++.h>
using namespace std;
int a[10];
int main() {
  int res = 0;
  for (int i = 1; i <= 3; ++i) {
    cin >> a[i];
    res += a[i];
  }
  res = res * 2 - 6;
  for (int i = 1; i < 3; ++i)
    for (int j = i + 1; j <= 3; ++j)
      if (a[i] > a[j]) {
        int temp = a[i];
        a[i] = a[j];
        a[j] = temp;
      }
  int ans = 0;
  while (a[1] > 1) {
    ans = 0;
    for (int i = 1; i <= 3; ++i) --a[i];
    if (a[1] != 1) {
      for (int i = 1; i <= 3; ++i) ans += a[i];
      ans = ans * 2 - 6;
    } else
      ans = a[2] * a[3];
    res += ans;
  }
  cout << res << endl;
  return 0;
}
