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