GCD

#include <iostream>

int GCD(int a, int b) {
  if (a == 0 || b == 0) throw std::runtime_error("Zero params for GCD");

  // Алгоритм Евклида
  while (true) {
    int r = a % b;
    if (r == 0) return b;
    a = b;
    b = r;
  }
}

int main() {
  int a = 0, b = 0;
  std::cin >> a >> b;

  std::cout << GCD(a, b);
  return 0;
}