#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, cnt = 0, m, k, i, j, t = 1, l, a, b;
  cin >> a >> b >> n;
  a = a * 10 - 1;
  for (i = 0; i < 10; i++) {
    a++;
    if (a % b == 0) {
      cnt = 1;
      break;
    }
  }
  if (cnt) {
    cout << a;
    for (i = 0; i < n - 1; i++) cout << 0;
  } else
    cout << -1;
  cout << endl;
  return 0;
}
