HDU2054 (see also GCD, water)

There are three positive integers a,b,c (0<a,b,c<10^6), where c is not equal to b. If the greatest common divisor of a and c is b, now a and b are known, find the smallest c that satisfies the condition. 

Input input an n in the first line, indicating that there are n groups of test data, the next n lines, each line input two positive integers a, b. 
Output outputs the corresponding c, and each set of test data occupies one line. 
Sample Input

2
6 2
12 4

Sample Output

4
8

code show as below:

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll gcd(ll a,ll b){
	while(b^=a^=b^=a%=b);
	return a;
}
int main(){
	int t;
	cin>>t;
	while(t--){
		ll a,b;
		cin>>a>>b;
		for(ll i=1;i<=a*b;i++){
			if(gcd(a,i)==b&&i!=b)
			{
				cout<<i<<endl;
				break;
			}
		}
	}
	return 0;
}