#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

ll p10[19];

int find_sol(ll a, int c, int m) {
  auto [g, x] = internal::inv_gcd(a, m);
  if (c % g) return -1;
  c /= g, m /= g;
  return c * x % m;
}

ll solve(string x, int m) {
  int n = x.size();
  rep(i, n) x[i] -= '0';
  for (int l = n; l <= 18; l++) {
    int d[18];
    rep(i, 18) d[i] = -1;
    rep(i, n) d[i] = x[i];
    int b = l - n;
    bool ok = true;
    rep(i, n) {
      if (d[b+i] != -1 && x[i] != d[b+i]) {
        ok = false;
        break;
      }
      d[b+i] = x[i];
    }
    if (!ok) continue;
    if (b <= n) {
      ll val = 0;
      rrep(i, l) val = 10 * val + d[i];
      if (val % m == 0) return val;
      continue;
    }
    ll c = 0;
    rrep(i, l) c = 10 * c + max(d[i], 0);
    ll cm = c % m;
    cm = (m - cm) % m;
    // 10^n t = cm (mod m)
    ll t = find_sol(p10[n], cm, m);
    if (t != -1 && t < p10[b - n]) {
      return c + p10[n] * t;
    }
  }
  return -1;
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  p10[0] = 1;
  rep(i, 18) p10[i+1] = p10[i] * 10;
  int tt;
  cin >> tt;
  while (tt--) {
    string x;
    int m;
    cin >> x >> m;
    reverse(all(x));
    cout << solve(x, m) << '\n';
  }
}