#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
long long a, b, n;
int main() {
  cin >> a >> b >> n;
  for (int i = 0; i <= 9; i++) {
    if ((a * 10 + i) % b == 0) {
      cout << a * 10 + i;
      while (n > 1) {
        cout << 0;
        n--;
      }
      cout << endl;
      return 0;
    }
  }
  puts("-1");
  return 0;
}
