#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define newl cout<<"\n";
#define space cout<<" ";
#define sz(x) x.size()
#define NumOfDigit(w) log10(w) + 1
#define MOD 1'000'000'007
#define inf 2'000'000'000
#define PI 3.141592654
#define modulo(a, b, mod) ((((a) % (mod)) + ((b) % (mod))) % (mod))
#define ceil(w, m) (((w) / (m)) + ((w) % (m) ? 1 : 0))
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define cin(v) for (auto&i:v) cin >> i;
#define cout(v) for (auto&i:v) cout << i << " ";
#define fixed(n) fixed << setprecision(n)
using namespace std;
void zainab_hamdy(){
  ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
  #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
  #endif
}
ll sum(ll n){
  return (n*(n+1))/2;
}

bool prime(ll n){
  if(n==2 || n==3) return true;
  if(n<2 || n%2==0  ) return false;
  for(int i=3;i<=sqrt(n);i+=2)   if(n%i==0) return false;
  return true;
}
bool cmp(ll right,ll left){
  return left<right;
}
ll GCD(ll a,ll b){
 ll x=a,y=b,res;
    while(1){
           ll tmp=y;
       y=x%y;
       x=tmp;
 if(y==0){
  res=x;
  break;
    }
 }
    return res;
}
 ll LCM(ll a,ll b){
    return (a/GCD(a,b))*b;
 }
void Solve(){
ll a,b,n; cin>>a>>b>>n;
ll freq[10]{};
for(int i=1;;i++){
  ll ans=(i*i*a)+(i*b);
  if(ans>n) break;
 if(ans<=n){
   while(ans){
     ll y=ans%10;
     freq[y]++;
     ans/=10;
   }
 }
}
ll mx=*max_element(freq,freq+10);
for(int i=1;i<10;i++){
if(freq[i]==mx && mx!=0){
  cout<<i;newl
  return;
}
}
cout<<"-1\n";
}
int main(){
  zainab_hamdy();
  int t=1;
 cin>>t;
     while(t--)
     Solve();
 return 0;
}