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, d=1, i;
  scanf("%d %d",&a, &b);
  if(a == b) {
    d = a;
  } else {
    a > b ? (c = a):(c = b);
    for(i = 1; i < c/2+1 ;i++) {
      if(a%i == 0 && b%i == 0) {
        d = i;
      }
    }
  }
  printf("%d\n",d);
  return 0;
}