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,cnt=0,n,i=1,flg =0;
    scanf("%d%d",&x,&y);
    if(x <= y){
        n = y/2;
        if(y % x ==0){
             flg = 1;
             cnt = x;
        }
    }else {
        n = x/2;
        if(x % y ==0){
            flg = 1;
            cnt = y;
        }
    }
    if(flg == 0){
        while(1){
            if(x%i==0&&y%i==0)   cnt = i;
            if(n == i) break;
            i++;
        }
    }
    printf("%d\n",cnt);
    return 0;
}