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 x,y,big,small,i;
  scanf(" %d %d",&x,&y);
  if(x < y){
    small = y;
    big = x;
  }
  else{
    small = x;
    big = y;
  }
  small = small % big;

  //printf("big = %d,small = %d\n",big,small);
  for(i = big; i > 0; i--){
    if(small % i == 0 && big % i == 0){
      printf("%d\n",i);
      break;
    }
  }
}