using System;

public class Program

{

    public static void Main()

    {

        int indice = -1;

        int numpesquisar = 7;

        int[] a= new int[] {3,7,3,9,2,6,7,8,9,2};

        for(int i = 0; i < a.Length;i++)

        {

            if (a[i] == numpesquisar )

            {

            indice = i;

            break;

            }

        }

    Console.WriteLine("Indice: {0}", indice);

    }

}