#include <bits/stdc++.h>
using namespace std;
int num_digits(int n) {
  int k = 0;
  while (n) {
    k++;
    n /= 10;
  }
  return k;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int a, b, n;
  cin >> a >> b >> n;
  int k = 0;
  while (((a * 10) + k) % b != 0 && k <= 9) {
    k++;
  }
  if (k == 10) k--;
  if (a % b == 0) {
    cout << a;
    for (int i = 0; i < n; i++) {
      cout << 0;
    }
    cout << "\n";
  } else if (((a * 10) + k) % b == 0) {
    cout << a << k;
    n--;
    for (int i = 0; i < n; i++) {
      cout << 0;
    }
    cout << "\n";
  } else {
    cout << -1 << "\n";
  }
}
