Gena loves sequences of numbers. Recently, he has discovered a new type of sequences which he called an almost arithmetical progression. A sequence is an almost arithmetical progression, if its elements can be represented as:

  * a1 = p, where p is some integer; 
  * ai = ai - 1 + ( - 1)i + 1·q (i > 1), where q is some integer. 



Right now Gena has a piece of paper with sequence b, consisting of n integers. Help Gena, find there the longest subsequence of integers that is an almost arithmetical progression.

Sequence s1, s2, ..., sk is a subsequence of sequence b1, b2, ..., bn, if there is such increasing sequence of indexes i1, i2, ..., ik (1 ≤ i1 < i2 < ... < ik ≤ n), that bij = sj. In other words, sequence s can be obtained from b by crossing out some elements.

Input

The first line contains integer n (1 ≤ n ≤ 4000). The next line contains n integers b1, b2, ..., bn (1 ≤ bi ≤ 106).

Output

Print a single integer — the length of the required longest subsequence.

Examples

Input

2
3 5


Output

2


Input

4
10 20 10 30


Output

3

Note

In the first test the sequence actually is the suitable subsequence. 

In the second test the following subsequence fits: 10, 20, 10.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.text.DecimalFormat;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.Queue;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
public class Main {
    int n;
    int[] b = new int[N], c = new int[N];
    int[][] dp = new int[N][N];
    TreeSet<Integer> set = new TreeSet();
    Iterator<Integer> it;
    Map<Integer,Integer> map = new TreeMap();
    void work() throws Exception{
        n = Int();
        for(int i = 1; i <= n; i++){b[i] = Int(); set.add(b[i]);}
        it = set.iterator();
        int len = 0;
        while(it.hasNext()){
            map.put(it.next(), ++len);
        }
        for(int i = 1; i <= n; i++) b[i] = map.get(b[i]);
    //  for(int i = 1; i <= n; i++)out.print(b[i]+" "); out.println();
        for(int i = 1; i <= n; i++)dp[1][i] = 1;
        int ans = 1;
        for(int i = 2; i <= n; i++){
            for(int j = 1; j <= n; j++)dp[i][j] = 1;
            for(int j = 1; j < i; j++){
                dp[i][b[j]] = max(dp[i][b[j]], dp[j][b[i]]+1);
                ans = max(ans, dp[i][b[j]]);
            }
        }
        out.println(ans);
    }

    public static void main(String[] args) throws Exception{
        Main wo = new Main();
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
  //    in = new BufferedReader(new InputStreamReader(new FileInputStream(new File("input.txt"))));
  //    out = new PrintWriter(new File("output.txt"));
        wo.work();
        out.close();
    }

    static int N = 4011;
    static int M = 1011;
    DecimalFormat df=new DecimalFormat("0.0000");
    static int inf = (int)1e9;
    static long inf64 = (long) 1e18;
    static double eps = 1e-8;
    static double Pi = Math.PI;
    static int mod = (int)1e9 + 7 ;
    
    private String Next() throws Exception{
        while (str == null || !str.hasMoreElements())
            str = new StringTokenizer(in.readLine());
        return str.nextToken();
    }
    private int Int() throws Exception{
        return Integer.parseInt(Next());
    }
    private long Long() throws Exception{
        return Long.parseLong(Next());
    }
    private double Double() throws Exception{
        return Double.parseDouble(Next());
    }
    StringTokenizer str;
    static Scanner cin = new Scanner(System.in);
    static BufferedReader in;
    static PrintWriter out;
  /*  
    class Edge{
        int from, to, dis, nex;
        Edge(){}
        Edge(int from, int to, int dis, int nex){
            this.from = from;
            this.to = to;
            this.dis = dis;
            this.nex = nex;
        }
    }
    Edge[] edge = new Edge[M<<1];
    int[] head = new int[N];
    int edgenum;
    void init_edge(){for(int i = 0; i < N; i++)head[i] = -1; edgenum = 0;}
    void add(int u, int v, int dis){
        edge[edgenum] = new Edge(u, v, dis, head[u]);
        head[u] = edgenum++;
    }/**/
    int upper_bound(int[] A, int l, int r, int val) {// upper_bound(A+l,A+r,val)-A;
        int pos = r;
        r--;
        while (l <= r) {
            int mid = (l + r) >> 1;
            if (A[mid] <= val) {
                l = mid + 1;
            } else {
                pos = mid;
                r = mid - 1;
            }
        }
        return pos;
    }
    int lower_bound(int[] A, int l, int r, int val) {// upper_bound(A+l,A+r,val)-A;
        int pos = r;
        r--;
        while (l <= r) {
            int mid = (l + r) >> 1;
            if (A[mid] < val) {
                l = mid + 1;
            } else {
                pos = mid;
                r = mid - 1;
            }
        }
        return pos;
    }
    int Pow(int x, int y) {
        int ans = 1;
        while (y > 0) {
            if ((y & 1) > 0)
                ans *= x;
            y >>= 1;
            x = x * x;
        }
        return ans;
    }
    double Pow(double x, int y) {
        double ans = 1;
        while (y > 0) {
            if ((y & 1) > 0)
                ans *= x;
            y >>= 1;
            x = x * x;
        }
        return ans;
    }
    int Pow_Mod(int x, int y, int mod) {
        int ans = 1;
        while (y > 0) {
            if ((y & 1) > 0)
                ans *= x;
            ans %= mod;
            y >>= 1;
            x = x * x;
            x %= mod;
        }
        return ans;
    }
    long Pow(long x, long y) {
        long ans = 1;
        while (y > 0) {
            if ((y & 1) > 0)
                ans *= x;
            y >>= 1;
            x = x * x;
        }
        return ans;
    }
    long Pow_Mod(long x, long y, long mod) {
        long ans = 1;
        while (y > 0) {
            if ((y & 1) > 0)
                ans *= x;
            ans %= mod;
            y >>= 1;
            x = x * x;
            x %= mod;
        }
        return ans;
    }

    int gcd(int x, int y){
        if(x>y){int tmp = x; x = y; y = tmp;}
        while(x>0){
            y %= x;
            int tmp = x; x = y; y = tmp;
        }
        return y;
    }
    int max(int x, int y) {
        return x > y ? x : y;
    }

    int min(int x, int y) {
        return x < y ? x : y;
    }

    double max(double x, double y) {
        return x > y ? x : y;
    }

    double min(double x, double y) {
        return x < y ? x : y;
    }

    long max(long x, long y) {
        return x > y ? x : y;
    }

    long min(long x, long y) {
        return x < y ? x : y;
    }

    int abs(int x) {
        return x > 0 ? x : -x;
    }

    double abs(double x) {
        return x > 0 ? x : -x;
    }

    long abs(long x) {
        return x > 0 ? x : -x;
    }

    boolean zero(double x) {
        return abs(x) < eps;
    }
    double sin(double x){return Math.sin(x);}
    double cos(double x){return Math.cos(x);}
    double tan(double x){return Math.tan(x);}
    double sqrt(double x){return Math.sqrt(x);}
}