#include <bits/stdc++.h>
using namespace std;
void show(vector<int> v) {
  for (auto it = v.begin(); it != v.end(); ++it) {
    cout << *it << " ";
  }
  cout << "\n";
}
void solve() {
  int a, b, n;
  cin >> a >> b >> n;
  int x = -1;
  for (int i = 0; i < 10; i++) {
    if ((a * 10 + i) % b == 0) {
      x = i;
      break;
    }
  }
  if (x == -1) {
    cout << -1;
    return;
  }
  cout << a << x;
  for (int i = 0; i < n - 1; i++) cout << 0;
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
