#include <bits/stdc++.h>
using namespace std;
inline void Boost() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
}
int main() {
  Boost();
  int a, b, n;
  cin >> a >> b >> n;
  for (int i = 0; i <= 9; ++i) {
    int x = a * 10 + i;
    if (x % b == 0) {
      cout << a << i;
      for (int j = 0; j < n - 1; ++j) cout << 0;
      return 0;
    }
  }
  cout << -1;
  return 0;
}
