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,d,remain,pregcd=0,gcd=0,i;
  scanf("%d %d",&x,&y);
  if(x>=y){
    remain=x%y;
    
    if(x>=remain){
      d=x;
    }
    else{
      d=remain;
    } 
    for(i=1;i<=d;i++){
      if(x%i==0 && remain%i==0){
	pregcd=i;
      }
      else {
	continue;
      }
      
      if(gcd<pregcd){
	gcd=pregcd;
      }
    }
  }
  
  if(y>=x){
    remain=y%x;
    
    if(y>=remain){
      d=y;
    }
    else{
      d=remain;
    }
    
    
    for(i=1;i<=d;i++){
      if(y%i==0 && remain%i==0){
	pregcd=i;
      }
      else {
	continue;
      }
      
      if(gcd<pregcd){
	gcd=pregcd;
      }
    }
  }
  printf("%d\n",gcd);

  return 0;
}