#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int a, b, n;
  cin >> a >> b >> n;
  if (a % b == 0) {
    cout << a;
    for (int i = 0; i < n; i++) {
      cout << "0";
    }
    cout << "\n";
    return 0;
  }
  int p;
  int digit = -1;
  for (int i = 0; i <= 9; i++) {
    p = a;
    p *= 10;
    p += i;
    if (p % b == 0) {
      digit = i;
      break;
    }
  }
  if (digit == -1) {
    cout << "-1\n";
  } else {
    cout << p;
    for (int i = 0; i < n - 1; i++) {
      cout << "0";
    }
    cout << "\n";
  }
}
