#include <bits/stdc++.h>
#include <random>
using namespace std;

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
#define rep3(i, a, b, c) for (ll i = (a); i < (b); i += (c))
#define rep2(i, a, b) rep3(i, a, b, 1)
#define rep1(i, n) rep2(i, 0, n)
#define rep0(n) rep1(aaaaa, n)
#define ov4(a, b, c, d, name, ...) name
#define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define per(i, a, b) for (ll i = (a) - 1; i >= (b); i--)
#define fore(e, v) for (auto &&e : v)
#define all(a) begin(a), end(a)
#define sz(a) (int)(size(a))
#define lb(v, x) (lower_bound(all(v), x) - begin(v))
#define eb emplace_back

template <typename T, typename S> bool chmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S> bool chmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}
const int INF = 1e9 + 100;
const ll INFL = 3e18 + 100;
#define i128 __int128_t
struct _ {
  _() { cin.tie(0)->sync_with_stdio(0), cout.tie(0); }
} __;

string solve(ll, ll);
int main() {
  int T;
  cin >> T;
  rep(T) {
    ll X, M;
    cin >> X >> M;
    cout << solve(X, M) << '\n';
  }
}

ll extGCD(ll a, ll b, ll &x, ll &y) {
  if (b == 0) {
    x = 1, y = 0;
    return a;
  }
  ll d = extGCD(b, a % b, y, x);
  y = y - a / b * x;
  return d;
}

string solve(ll X, ll M) {
  int xlen=1;
  if(X>=10)xlen++;
  if(X>=100)xlen++;
  ll d2 = 1,c2=0;
  while (M % (d2 * 2) == 0) {
    d2 *= 2;
    c2++;
  }
  ll d5 = 1,c5=0;
  while (M % (d5 * 5) == 0) {
    d5 *= 5;
    c5++;
  }
  while(c2>xlen)c2--,d2/=2;
  while(c5>xlen)c5--,d5/=5;
  if(X%(d2*d5)!=0){
    return "-1";
  }

  ll K = X * (1'000'000'000'000'000ll + 1) % M;
  ll x = 0, y = 0;

  if(xlen==3){

    extGCD(1000, M, x, y);
    ll c = (-x * K / gcd(1000, M) % M + M) % M;
    return format("{}{:012}{:03}", X, c, X);
  }else if(xlen==2){
    extGCD(100, M, x, y);
    ll c = (-x * K / gcd(100, M) % M + M) % M;
    return format("{}{:013}{:02}", X, c, X);
  }else{
    extGCD(10, M, x, y);
    ll c = (-x * K / gcd(10, M) % M + M) % M;
    return format("{}{:014}{:01}", X, c, X);
  }
}