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import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(in.hasNextInt())
        {
            int N=in.nextInt();
            int[] arr=new int[N];
            for(int i=0;i<N;++i)
                arr[i]=in.nextInt();
            int res=0;
            for(int i=0;i<N;++i)
            {
                for(int j=i+1;j<N;++j)
                {
                    for(int m=0;m<N;++m)
                    {
                        for(int n=m+1;n<N;++n)
                        {
                            if(!(i==m||i==n||j==m||j==n))
                            {
                                if(arr[i]+arr[j]==arr[m]+arr[n])
                                    ++res;
                            }
                        }
                    }
                }
            }
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