#include <bits/stdc++.h>
using namespace std;
int main() {
  long long a, b, n;
  cin >> a >> b >> n;
  long long r = (10 * a) % b;
  if (r != 0) {
    if (b - r >= 10) {
      cout << "-1\n";
      return 0;
    } else {
      a = 10 * a + (b - r);
      --n;
    }
  }
  cout << to_string(a);
  for (int i = 0; i < n; ++i) {
    cout << "0";
  }
  cout << '\n';
}
