#include <bits/stdc++.h>
using namespace std;
const long long maxn = 500005;
const long long mod = 1e9 + 7;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int a, b, n, num, f = 0, i;
  cin >> a >> b >> n;
  string ans;
  for (i = 0; i <= 9; ++i) {
    if ((10 * a + i) % b == 0) {
      f = 1;
      num = 10 * a + i;
      break;
    }
  }
  if (f) {
    ans = to_string(num);
    string temp(n - 1, '0');
    ans += temp;
    cout << ans;
  } else
    cout << -1;
}
