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: Accepted)

#include<stdio.h>
#define min(a,b)((a) < (b) ? (a) : (b))

int gcd(int, int);

int main(){
  int i,j;

  scanf("%d%d",&i,&j);

  if(i >= j){
    printf("%d\n",gcd(j,i % j));
  }

  if(i < j){
    printf("%d\n",gcd(i,j % i));
  }
      
  return 0;
}

int gcd(int a, int b){
  int n,d;
  
  n = min(a,b);
  
  for(d = n; d >= 1; d--){
    if(a % d == 0 && b % d == 0){
      return d;
    }   
  }
  return a;

}