Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length N, a_1,a_2,...,a_N.

For each 1≤i≤N, you have three choices: add 1 to a_i, subtract 1 from a_i or do nothing.

After these operations, you select an integer X and count the number of i such that a_i=X.

Maximize this count by making optimal choices.

Constraints

1≤N≤10^5

0≤a_i<10^5 (1≤i≤N)

a_i is an integer.

Input

The input is given from Standard Input in the following format:

N
a_1 a_2 .. a_N

Output

Print the maximum possible number of i such that a_i=X.

Sample Input 1

7
3 1 4 1 5 9 2

Sample Output 1

4

For example, turn the sequence into 2,2,3,2,6,9,2 and select X=2 to obtain 4, the maximum possible count.

Sample Input 2

10
0 1 2 3 4 5 6 7 8 9

Sample Output 2

3

Sample Input 3

1
99999

Sample Output 3

1

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

//#define _GLIBCXX_DEBUG
#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef long double ld;

#define mk make_pair
#define inb push_back
#define X first
#define Y second
#define all(v) v.begin(), v.end()
#define sqr(x) (x) * (x)
#define TIME 1.0 * clock() / CLOCKS_PER_SEC
#define y1 AYDARBOG
//continue break pop_back return

int solve();

int main()
{
    //ios_base::sync_with_stdio(0);
    //cin.tie(0);
#define TASK "lzss"
#ifndef _DEBUG
    //freopen(TASK".in", "r", stdin), freopen(TASK".out", "w", stdout);
#endif
    solve();
#ifdef _DEBUG
    fprintf(stderr, "\nTIME: %.3f\n", TIME);
#endif
}

int solve()
{
    int n;
    scanf("%d", &n);
    int MAXN = (int)1e5 + 2;
    vi cnt(MAXN);
    for (int i = 0; i < n; ++i)
    {
        int x;
        scanf("%d", &x);
        cnt[x]++;
    }
    int ans = 0;
    for (int i = 1; i <= 99999; ++i)
        ans = max(ans, cnt[i - 1] + cnt[i] + cnt[i + 1]);
    printf("%d\n", ans);
    return 0;
}