#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int t;
  t = 1;
  while (t--) {
    int a, b, n, k, flag = 0, l;
    cin >> a >> b >> n;
    for (int i = 0; i <= 9; i++) {
      if ((a * 10 + i) % b == 0) {
        flag++;
        l = i;
      }
    }
    if (flag == 0)
      cout << -1;
    else if (b == 10) {
      cout << a;
      while (n) {
        cout << 0;
        n--;
      }
    } else if (l == 0) {
      cout << a;
      while (n) {
        cout << 0;
        n--;
      }
    } else {
      cout << a;
      a = a * 10;
      k = b - a % b;
      cout << k;
      n--;
      while (n) {
        cout << 0;
        n--;
      }
    }
  }
  cerr << "Time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
  return 0;
}
