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(void){

    char tmp =0;
    int num1,num2,answer =0;
    
    while( (tmp = getchar()) != ' ' )
    {
        if( '0' <= tmp <= '9' )
        {
            num1 = (num1 * 10) + (tmp - '0');
        }
    };
    
    while( (tmp = getchar()) != '\n' )
    {
        if( '0' <= tmp <= '9' )
        {
            num2 = (num2 * 10) + (tmp - '0');
        }
    };
    
    while(answer == 0){
        if(num2==num1)
        {
            answer = num1;
        }
        else if (num2>num1)
        {
            num2=num2%num1;
            if(num2==0)
            {
                answer = num1;
            }
        }
        else
        {
            num1=num1%num2;
            if(num1==0)
            {
                answer = num2;
            }
        }
    }
    printf("%d\n",answer);
    
    return 0;
}