#include <bits/stdc++.h>
using namespace std;
inline int gcd(int a, int b) {
  while (1) {
    a = a % b;
    if (a == 0) return b;
    b = b % a;
    if (b == 0) return a;
  }
}
const int maxN = 15;
const int inf = 1e9;
int n, a, b;
inline void init() { scanf("%d%d%d", &a, &b, &n); }
inline void solve() {
  long long tmp = (long long)a * 10;
  int i = -1;
  bool f = false;
  for (i = 0; i < 10; i++) {
    if ((tmp + i) % b == 0) {
      f = true;
      break;
    }
  }
  if (f == false)
    printf("-1");
  else {
    printf("%d", a);
    printf("%d", i);
    n--;
    while (n--) {
      printf("0");
    }
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  init();
  solve();
  return 0;
}
