#include <bits/stdc++.h>
using namespace std;
int main() {
  long long a, b, n;
  cin >> a >> b >> n;
  int flag = 0;
  for (int p = 0; p <= 9; p++) {
    if ((a * 10 + p) % b == 0) {
      a = a * 10 + p;
      flag = 1;
      break;
    }
  }
  n--;
  if (flag == 0) {
    cout << -1 << "\n";
    return 0;
  }
  string sec = "";
  string fir = "";
  fir = fir + to_string(a);
  while (n--) {
    sec = sec + "0";
  }
  fir = fir + sec;
  cout << fir << "\n";
}
