using System;

class Test {
  
  static int IndexOf(int val, int[] tab) {
    int i = tab.Length - 1;
    while (i >= 0 && tab[i] != val) i--;
    return i;
  }
  
  static void Main() {
    int[] tab = {3, 6, 14, 4, 12, 9, 10, 1, 5};
    Console.WriteLine(IndexOf(3, tab));
    Console.WriteLine(IndexOf(5, tab));
    Console.WriteLine(IndexOf(12, tab));
    Console.WriteLine(IndexOf(7, tab));
  }
  
}