/*

1. x が接尾辞と接頭辞として被るケース

2. 被らないケース

*/
#include<bits/stdc++.h>
#include<atcoder/math>
using namespace std;
using ll = long long;

int presuf(string s, int len){
    int sz = s.size();
    assert(sz <= len && len <= sz * 2);
    s += s.substr(sz*2-len);
    return stoi(s);
}

ll ten(int e){
    ll ret = 1;
    while (e--){
        ret *= 10;
    }
    return ret;
}

void solve(){
    int x; cin >> x;
    int m; cin >> m;
    string s = to_string(x);
    int sz = s.size();
    for (int len = sz; len <= sz*2; len++){
        int v = presuf(s,len);
        if (v % m == 0){
            cout << v << '\n';
            return ;
        }
    }
    for (int len = sz*2+1; len <= 18; len++){
        ll a = ten(sz);
        ll b = (ten(len-sz)+1)*x;
        // an + b == mk
        a %= m;
        b %= m;
        ll g = gcd(a, m);
        if (b % g != 0) continue;
        // a/g n + b/g == m/g k
        ll n = atcoder::internal::safe_mod(atcoder::inv_mod(a/g,m/g) * (-b/g), m/g);
        if (n < ten(len-2*sz)){
            ll v = a * n + b;
            cout << v << '\n';
            return ;
        }
    }
    cout << -1 << '\n';
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    int t; cin >> t;
    while (t--){
        solve();
    }
}