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