我真棒

#include <iostream>
#include <cstring>
using namespace std;
int gcd(int m, int n){
    if(n == 0){
        return m;
    }else{
        return gcd(n, m % n);
    }
}
bool chase(char p[], int l, int n){
    for(int i = 0; i < l - n; ++i){
        if(p[i] != p[i + n]){
            return false;
        }
    }
    return true;
}
bool evan(char p[], char q[], int n){
    for(int i = 0; i < n; ++i){
        if(p[i] != q[i]){
            return false;
        }
    }
    return true;
}
void found(){
    char s[30], s1[30];
    cin >> s >> s1;
    int a = strlen(s), b = strlen(s1), d = gcd(a, b);
    for(int i = d; i > 0; --i){
        if(d % i == 0 && chase(s, a, i) == true && chase(s1, b, i) == true && evan(s, s1, i) == true){
            for(int j = 0; j < b / d; ++j){
                cout << s;
            }
            cout << endl;
            return ;
        }
    }
    cout << -1 << endl;
}
int main(){
    int t;
    cin >> t;
    for(int i = 0; i < t; ++i){
        found();
    }
    return 0;
}