#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;
}

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