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