#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int a, b, n, m = 1;
  cin >> a >> b >> n;
  long long int rs = b - ((a * 10) % b);
  if (rs < 10) {
    a = (a * 10) + rs;
  } else if (rs == b) {
    a = (a * 10);
  } else {
    a = 0;
  }
  if (a != 0) {
    cout << a;
    while (n != 1) {
      cout << 0;
      n--;
    }
  } else {
    cout << -1;
  }
  return 0;
}
