#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, n, i, j, s, p = 0;
  cin >> a >> b >> n;
  if (a % b != 0) {
    for (i = 0; i < 10; i++) {
      s = a * 10 + i;
      if (s % b == 0) {
        p = 1;
        break;
      }
    }
    if (p == 1) {
      if (n == 1) {
        printf("%d\n", s);
      } else {
        n--;
        printf("%d", s);
        while (n--) {
          cout << 0;
        }
        cout << endl;
      }
    } else
      printf("-1\n");
  } else {
    cout << a;
    while (n--) {
      cout << 0;
    }
    cout << endl;
  }
  return 0;
}
