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(void) {
    int a,b,c,i;
    scanf("%d %d",&a,&b);

    if (a < b) {
      for (i = 1; i <= a; i++) {
        if (a % i == 0 && b % i == 0)
          c = i;
        }
    }
    else {
      for (i = 1; i <= b; i++) {
        if (a % i == 0 && b % i == 0)
          c = i;
        }
    }

    printf("%d\n",c);

    return 0;
}