#include <bits/stdc++.h>
using namespace std;
int main() {
  long long a, b, n;
  cin >> a >> b >> n;
  long long ct = a;
  int flag = 0;
  for (int i = 0; i < 10; i++) {
    ct *= 10;
    ct += i;
    if (ct % b == 0) {
      flag = 1;
      break;
    } else {
      ct -= i;
      ct /= 10;
    }
  }
  if (flag != 1) {
    cout << "-1";
  } else {
    cout << ct;
    for (long long j = 0; j < (n - 1); j++) {
      cout << "0";
    }
  }
}
