Problem:
Greatest Common Divisor

Write a program which finds the greatest common divisor of two natural numbers a and b

Input

a and b are given in a line sparated by a single space.

Output

Output the greatest common divisor of a and b.

Constrants

1 ≤ a, b ≤ 109

Hint

You can use the following observation:

For integers x and y, if x ≥ y, then gcd(x, y) = gcd(y, x%y)

Sample Input 1

54 20

Sample Output 1

2

Sample Input 2

147 105

Sample Output 2

21

Solution in C (judge verdict: Time Limit Exceeded)

#include<stdio.h>

int main(){
  unsigned long x,y,n,d;
  
  scanf("%ld%ld",&x,&y);

  if(x>y){
    n=y;
  }else{
    n=x;
  }
  
  for(d=n;d>0;d--){
    if(x%d==0&&y%d==0){
      printf("%ld\n",d);
      break;
    }
  }
  return 0;
}