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