#include <bits/stdc++.h>
using namespace std;
int func(long int temp) {
  int digits = 0;
  while (temp != 0) {
    temp = temp / 10;
    digits++;
  }
  return digits;
}
int main() {
  long int a, b, n;
  cin >> a >> b >> n;
  int flag = 0;
  long int ans = 10 * a;
  for (int i = 0; i <= 9; i++) {
    if (ans % b == 0) {
      flag++;
      break;
    }
    ans++;
  }
  if (flag != 0) {
    cout << ans;
    for (int i = 0; i < n - 1; i++) cout << "0";
  } else
    cout << "-1";
}
