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

using ll=long long;
pair<ll,ll> extgcd(ll a,ll b){
  if (b==0) return {1,0};
  auto [y,x]=extgcd(b,a%b);
  y-=a/b*x;
  return {x,y};
}
ll f(ll a,ll b,ll mod){
  ll g=gcd(gcd(a,b),mod);
  a/=g;
  b/=g;
  mod/=g;
  ll g2=gcd(a,mod);
  if (g2==1) return (extgcd(a,mod).first*b)%mod;
  else return -1;
}

void solve(){
  vector<ll> ten(20);
  ten[0]=1;
  for (int i=1;i<20;i++) ten[i]=ten[i-1]*10;
  string x;
  ll m;
  cin>>x>>m;
  int nx=x.size();
  for (int nz=0;nz+nx*2<=18;nz++){
    ll p=ten[nx+nz]+ten[0];
    ll b=((-p*stoll(x))%m+m)%m;
    ll a=ten[nx];
    ll z=f(a,b,m);
    if (z!=-1){
      string z2=to_string(z);
      if (nz<z2.size()) continue;
      while (nz>z2.size()) z2="0"+z2;
      string ans=x+z2+x;
      cout<<ans<<endl;
      return;
    }
  }
  auto check=[&](string s){
    int n=s.size();
    bool ok=stoll(s)%m==0;
    for (int i=0;i<nx;i++){
      ok&=s[i]==x[i];
      ok&=s[n-nx+i]==x[i];
    }
    return ok;
  };
  for (int i=0;i<nx;i++){
    string ans=x;
    for (int j=i;j<nx;j++) ans+=x[j];
    if (check(ans)){
      cout<<ans<<endl;
      return;
    }
  }
  cout<<-1<<endl;
}

int main(){
  int t;
  cin>>t;
  while (t--) solve();
}