#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n;
  cin >> a >> b >> n;
  a = a * 10;
  int f = 0;
  for (int i = 0; i < 10; i++) {
    if ((a + i) % b == 0) {
      cout << a + i;
      string s(n - 1, '0');
      cout << s << endl;
      f = 1;
      break;
    }
  }
  if (!f) cout << -1 << endl;
}
