Problem Statement

You are given positive integers X and Y. If there exists a positive integer not greater than 10¹⁸ that is a multiple of X but not a multiple of Y, choose one such integer and print it. If it does not exist, print −1.

Constraints

• 1≤X,Y≤10⁹
• X and Y are integers.

Sample Input 1

8 6

Sample Output 1

16

For example, 16 is a multiple of 8 but not a multiple of 6.

Sample Input 2

3 3

Sample Output 2

-1

A multiple of 3 is a multiple of 3.

只需要判断x是否是y的倍数。

代码：

#include <iostream>

#include <algorithm>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <cmath>

#include <iomanip>

using namespace std;

int a,b;

int main()

{

    cin>>a>>b;

    if(a % b)cout<<a;

    else cout<<-;

}