#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int a, b, n, x;
  cin >> a >> b >> n;
  bool ok = 0;
  string s = "";
  for (int i = 0; i < 10; i++) {
    if ((10 * a + i) % b == 0) {
      ok = 1;
      x = i;
      break;
    }
  }
  if (!ok) return cout << "-1\n", 0;
  cout << a << x;
  for (int i = 1; i < n; i++) cout << 0;
  cout << "\n";
  return 0;
}
