#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long a, b, n;
  cin >> a >> b >> n;
  long long r = a % b;
  for (long long i = 0; i <= 9; i++) {
    if ((r * 10 + i) % b == 0) {
      cout << a;
      cout << i;
      for (long long i = 0; i < n - 1; ++i) {
        cout << 0;
      }
      return 0;
    }
  }
  cout << (-1) << "\n";
  return 0;
}
