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 a,b,c,d;
  scanf("%d%d",&a,&b);
  if(a>b){
    d=a%b;
    while(d!=0){
      a=b;
      b=d;
      d = a%b;
    }
    printf("%d",b);
  }
  else if(a<b){
    d=b%a;
    while(d!=0){
      b=a;
      a=d;
      c = a%d;
    }
    printf("%d",a);
  }
  else{
    printf("%d",a);
  }
  printf("\n");
  return 0;
}