#include <bits/stdc++.h>
using namespace std;
template <class T>
T fm(T number, T module) {
  T result = 1;
  while (number > 1) {
    result = (result * ((number / module) % 2 ? module - 1 : 1)) % module;
    for (T i = 2; i <= (number % module); ++i) {
      result = (result * i) % module;
    }
    number /= module;
  }
  return result % module;
}
template <class T>
T lcm(T a, T b) {
  return (a * b / gcd(a, b));
}
int main(int argc, char *argv[]) {
  std::ios_base::sync_with_stdio(false);
  unsigned a(0), b(0), n(0);
  cin >> a >> b >> n;
  for (unsigned it(0); it != 10; ++it) {
    if (!((a * 10 + it) % b)) {
      cout << a << it;
      for (--n; n > 0; --n) {
        cout << 0;
      }
      return 0;
    }
  }
  cout << "-1";
  return 0;
}
