using System;

public class Program

{

    public static void Main()

    {

        int[] source ={1,2,3,4,3,4,5,6,7,8};

        int[] target ={3,4,5,6};

        int j=0;

        int index=0;

        bool match= false;

        for(int i=0;i< source.Length && j< target.Length;)

        {

            if(source[i]!= target[j])

            {

                if(match==true)

                {

                    j=0;

                    index=i;

                }

                else

                {

                    i++;                

                    j=0;

                    index=i;    

                }

            }

            else

            {

                match=true;

                i++;                

                j++;

            }

        }

        if(j==target.Length)

                Console.WriteLine(index);

        else

                    Console.WriteLine(-1);

​

    }

}