#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const *argv[]) {
  int a, b;
  int n;
  cin >> a >> b >> n;
  bool aoa = false;
  for (int i = 0; i <= 9; i++) {
    int k = a;
    k = k * 10;
    k += i;
    if (k % b == 0) {
      aoa = true;
      a = k;
      break;
    }
  }
  if (aoa == false)
    cout << -1;
  else {
    cout << a;
    for (int i = 0; i < n - 1; i++) cout << 0;
    return 0;
  }
}
