#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  int a, b, n;
  cin >> a >> b >> n;
  a = a * 10;
  n--;
  int count = 0;
  int flag = 0;
  while (count <= 9) {
    if ((a + count) % b == 0) {
      a += count;
      flag = 1;
      break;
    } else {
      flag = 0;
    }
    count++;
  }
  if (flag) {
    cout << a;
    while (n--) {
      cout << '0';
    }
  } else {
    cout << -1;
  }
}
