#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void solve() {
  int a, b, n, t, i;
  cin >> a >> b >> n;
  t = a * 10;
  for (i = 0; i <= 9; i++)
    if ((t + i) % b == 0) break;
  if (i > 9) {
    cout << -1 << '\n';
    return;
  }
  cout << (t + i);
  for (int i = 1; i < n; i++) cout << 0;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int test = 1;
  while (test--) solve();
  return 0;
}
