#include <bits/stdc++.h>
using namespace std;
int main(int argc, char** argv) {
  int a, b, n;
  cin >> a >> b >> n;
  int na = a * 10;
  for (int i = 0; i < 10; i++) {
    int num = na + i;
    if (num % b == 0) {
      cout << num;
      for (int j = 0; j < n - 1; j++) {
        cout << 0;
      }
      cout << endl;
      return 0;
    }
  }
  cout << -1 << endl;
}
