#include <bits/stdc++.h>
int main(void) {
  int a, b, n, i;
  scanf("%d %d %d", &a, &b, &n);
  if (i = (10 * a + 9) % b, i < 10) {
    printf("%d%d", a, 9 - i);
    for (i = 1; i < n; ++i) {
      printf("0");
    }
  } else {
    printf("-1");
  }
  printf("\n");
  exit(EXIT_SUCCESS);
}
