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>

int main(){
  int a,b,x,y,i,ans=0;

  scanf("%d%d",&a,&b);

  if(a==b){
    printf("%d\n",a);
    return 0;
  }
  else if(a>b){
    x = b;
    y = a%b;
  }
  else if(b>a){
    y = b%a;
    x = a;
  }
  
  for(i=1;i<=y;i++){
    if(x%i==0 && y%i==0)ans=i;
  }

  printf("%d\n",ans);

  return 0;
}