#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n;
  cin >> a >> b >> n;
  int first = 0;
  bool f = false;
  while (first < 10) {
    if ((10 * a + first) % b == 0) {
      f = true;
      break;
    }
    first++;
  }
  if (!f) {
    cout << -1 << endl;
    return 0;
  }
  cout << a << first;
  for (int i = 0; i < n - 1; ++i) cout << 0;
  cout << endl;
  return 0;
}
