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 x,y,ans;
  scanf("%d%d",&x,&y);
  if(x<=0||y<=0||x>1000000001||y>1000000001){
    return 0;
  }
  int i;
  for(i=1;x>=i && y>=1;i++){
    if(x%i==0&&y%i==0)ans=i;
  }
  printf("%d\n",ans);
  return 0;
}