#include <bits/stdc++.h>
using namespace std;
string solve() {
  int a, b, n;
  string number = "";
  cin >> a >> b >> n;
  bool added;
  added = false;
  a *= 10;
  for (int j = 1; j < 11; j++) {
    if (a % b == 0) {
      added = true;
      break;
    }
    a++;
  }
  if (!added) return "-1";
  number = to_string(a);
  for (int i = 0; i < n - 1; i++) number += '0';
  return number;
}
int main(void) { cout << solve() << "\n"; }
