2
6 2
12 4

4
8

AC代码:

#include <iostream>
using namespace std;
int GCD(int x,int y)
{
    return y==0?x:GCD(y,x%y);
}
int main()
{
    int t,a,b;
    cin>>t;
    while(t--)
    {
        cin>>a>>b;
        int c = 2*b;
        while(GCD(a,c)!=b)
        {
            c+=b;
        }
        cout<<c<<endl;
    }
    return 0;
}