#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n;
  cin >> a >> b >> n;
  a *= 10;
  int aa = (a % b);
  aa = ((b - aa) % b + b) % b;
  if (aa <= 9) {
    a += aa;
    cout << a;
    for (int i = 1; i <= n - 1; i++) putchar('0');
  } else
    cout << -1 << endl;
}
