#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  unsigned long long int a, b, n, x, c, i;
  cin >> a >> b >> n;
  int flag = 0;
  for (i = 1; i <= n; i++) {
    a = (a * 10);
    x = a % b;
    c = (b - x);
    if (x == 0) {
      break;
    }
    if (c % 10 == c) {
      a = a + c;
      break;
    } else {
      flag = 1;
      break;
    }
  }
  string s;
  s = to_string(a);
  if (flag == 0) {
    for (i = 2; i <= n; i++) {
      s.push_back('0');
    }
    cout << s << "\n";
  } else {
    cout << "-1" << endl;
  }
  return 0;
}
