#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n;
  scanf("%d %d %d", &a, &b, &n);
  a *= 10;
  for (int i = 0; i <= 9; i++) {
    int x = a;
    x += i;
    if (x % b == 0) {
      n--;
      cout << x;
      for (int j = 0; j < n; j++) {
        cout << 0;
      }
      return 0;
    }
  }
  cout << -1 << endl;
  return 0;
}
