#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:1000000000")
using namespace std;
int main() {
  long long a, b, n;
  cin >> a >> b >> n;
  bool f = false;
  for (long long i = 0; i < 10; ++i) {
    if ((a * 10 + i) % b == 0) {
      a = a * 10 + i;
      f = true;
      break;
    }
  }
  if (!f)
    cout << -1;
  else {
    cout << a;
    for (long long i = 0; i < n - 1; ++i) cout << 0;
  }
}
