#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n, j, temp, num;
  stringstream s, t;
  cin >> a >> b >> n;
  string out;
  s << a;
  num = a;
  for (j = 0; j < 10; j++) {
    s << j;
    s >> temp;
    if (temp % b == 0) {
      num = temp;
      s.clear();
      s << num;
      break;
    } else {
      s.clear();
      s << num;
    }
  }
  if (j == 10)
    cout << -1;
  else {
    for (int i = 0; i < n - 1; i++) s << '0';
    s >> out;
    cout << out;
  }
  return 0;
}
