#include <bits/stdc++.h>
using namespace std;
long long a, b, n;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> a >> b >> n;
  for (long long x = 0; x < 10; x++) {
    long long t = a * 10 + x;
    if (t % b == 0) {
      cout << t;
      for (long long x = 0; x < n - 1; x++) cout << 0;
      cout << '\n';
      return 0;
    }
  }
  cout << -1 << '\n';
  return 0;
}
