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, i, key;
  scanf("%d %d",&a,&b);
  if(a < b)i = a;
  else i = b;
  
  for(; i>=1 ;i--){
    if(a%i==0 && b%i==0){
      key = i;
      break;
    }
  }
  /*
    for(i=1; i<=a || i<=b; i++){
    if(a%i==0 && b%i==0)
    key = i;
    }*/
  printf("%d\n",key);
  return 0;
}