#include <bits/stdc++.h>
using namespace std;
int a, b, n;
int main() {
  while (scanf("%d%d%d", &a, &b, &n) != EOF) {
    int sum = a, k = a, i, flag = 1;
    for (int j = 0; j <= 9; j++) {
      k = sum;
      k = k * 10 + j;
      if (k % b == 0) {
        flag = 0;
        break;
      }
    }
    if (flag == 0) {
      printf("%d", k);
      for (i = 1; i < n; i++) {
        printf("0");
      }
      printf("\n");
    } else
      printf("-1\n");
  }
  return 0;
}
