#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios::sync_with_stdio(false);
  int a, b, n, x;
  cin >> a >> b >> n;
  bool found = false;
  for (int j = 0; j <= 9; ++j) {
    x = 10 * a + j;
    if (x % b == 0) {
      a = x;
      found = true;
      break;
    }
  }
  if (!found) {
    cout << -1 << endl;
    return 0;
  }
  cout << a << string(n - 1, '0') << endl;
}
