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