A. Restoring Numbers

A. Restoring Numbers

					time limit per test  2.0 s
					memory limit per test  256 MB

Pavel had two positive integers a and b. He found their sum s and greatest common divisor g, and forgot a and b after that. Help him to restore the original numbers.
Input

A single line contains two integers s and g (1 ≤ s ≤ 109, 1 ≤ g ≤ 109) — sum and greatest common divisor of the numbers a and b.

Output

If Pavel made a mistake and there are no such numbers a and b, output a single number  - 1.

Otherwise, output two positive integers a and b on a single line, separated by a space. If there are multiple possible solutions, output any of them.
解析：
如果使用暴力的做法会导致超时，卡第21个样例过不去，所以我们优化一下算法，令其中一个数字a的值为g，那么如果g和s - g的g为题干中输入的g那么输出符合的结果，否则一定不会存在这个值a和b
My Solution

#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b )
{
    
    
    return b ? gcd(b, a % b ) : a;
}
int main()
{
    
    
    long long s, g, k;
    cin >> s >> g;
    if(gcd(g, s - g) == g && s != g)
        cout << max(g, s - g) << " " << min(g, s - g) << endl;
    else cout << "-1" << endl;
    return 0;
}