#include "stdio.h"

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

int main()
{
  int a;
  a = gcd(5, 15);
  printf("%d", a);
  return 0;
}