#include <bits/stdc++.h>
using namespace std;
void setup() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout.precision(15);
}
int main() {
  setup();
  int a, b, n, flag = 0, k, i;
  cin >> a >> b >> n;
  for (k = a * 10; k <= a * 10 + 9; k++) {
    if (k % b == 0) break;
  }
  if (k == a * 10 + 10)
    cout << -1;
  else {
    cout << k;
    for (i = 0; i < n - 1; ++i) cout << 0;
  }
}
