#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n;
  scanf("%d %d %d", &a, &b, &n);
  a *= 10;
  int c = a % b;
  c = b - c;
  if (c == b) c = 0;
  if (c < 10)
    a += c;
  else
    return printf("-1"), 0;
  printf("%d", a);
  while (--n) {
    cout << "0";
  }
  return 0;
}
