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