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(){
  int a, b, n, i;
  scanf("%d %d",&a,&b);
  if( a > b ) n = b;
  else n = a;
  for( i = n ; i >= 1 ; i-- ){
    if( a % i == 0  && b % i == 0 ) break;
  }
  printf("%d\n",i);
  return 0;
}