#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  long long int a, b, n;
  cin >> a >> b >> n;
  for (long long int i = 0; i < 10; i++) {
    if ((10 * a + i) % b == 0) {
      cout << a << i;
      for (long long int i = 0; i < n - 1; i++) {
        cout << 0;
      }
      return 0;
    }
  }
  cout << -1;
}
