#include <iostream>

using namespace std;

int main() {
  long long N, K, L;
  cin >> N >> K >> L;

  // Calculate the total area of all squares
  long long totalArea = N * L * K;

  // Calculate the area of overlap (the area of the last square that doesn't overlap)
  long long overlapArea = (N - 1) * L * K; 

  // Calculate the area of the union
  long long unionArea = totalArea - overlapArea;

  cout << unionArea << endl;

  return 0;
}