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