#include <stdio.h>

int gcd(int a, int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}

int main() {
  for (int a = 10; a <= 15; a++) {
    for (int b = 16; b <= 20; b++) {
      printf("a=%d b=%d gcd(a, b)=%d\n", a, b, gcd(a, b));
    }
  }
}