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

using ll=long long;
using lll=__int128_t;
lll modinv(lll a, lll m) {
    lll b = m, u = 1, v = 0;
    while (b) {
        lll t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m; 
    if (u < 0) u += m;
    return u;
}
lll f(lll a,lll b,lll mod){
  lll g=gcd(gcd(a,b),mod);
  a/=g;
  b/=g;
  mod/=g;
  if (gcd(a,mod)==1) return (modinv(a,mod)*b)%mod;
  else return -1;
}

void solve(){
  vector<lll> 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++){
    lll p=ten[nx+nz]+ten[0];
    lll b=((-p*stoll(x))%m+m)%m;
    lll 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;
      assert(stoll(ans)%m==0);
      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;
      assert(stoll(ans)%m==0);
      return;
    }
  }
  cout<<-1<<endl;
}

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