#include <bits/stdc++.h>
using namespace std;
template <class c>
struct rge {
  c b, e;
};
template <class c>
rge<c> range(c i, c j) {
  return rge<c>{i, j};
}
template <class c>
auto dud(c* x) -> decltype(cerr << *x, 0);
template <class c>
char dud(...);
struct deb {
  template <class c>
  deb& operator<<(const c&) {
    return *this;
  }
};
long long pow(long long v, long long k) {
  long long ans = 1;
  while (k--) {
    ans *= v;
  }
  return ans;
}
void solution() {
  unsigned long long int a, b, n;
  cin >> a >> b >> n;
  a *= 10;
  unsigned long long int rem = b - (a % b);
  if (a % b == 0) {
    rem = 0;
  }
  if (rem > 9) {
    cout << -1 << "\n";
    return;
  }
  a += rem;
  cout << a;
  for (int i = 0; i < n - 1; i++) {
    cout << "0";
  }
  cout << "\n";
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int T = 1;
  for (int tt = 1; tt <= T; tt++) {
    solution();
  }
  return 0;
}
