#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

int cmp(const void* a,const void* b)
    {
    const int* ai= (int *)a;
    const int* bi= (int *)b;
    return (*ai-*bi);
}

int main(){
    int n;
    cin >> n;
    int f[n];
    int* a = (int *)malloc(n*sizeof(int));
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        f[a_i]=0;
    }
    qsort(a,n,sizeof(int),cmp);
    int ans,mf,mpos,k;int c[n];
    c[0]=a[0];f[0]=1;k=0;mpos = 0;mf = 1;ans=0;
    for(int i = 1;i < n;i++){
        if(a[i] == a[i-1])
            f[k]++;
        else
            {
            if(f[k] > mf)
                {
                mf = f[k];
                mpos = k;
            }
            if(k>=1)
                {
                if((c[k]-c[k-1] == 1) || (c[k]-c[k-1] == -1))
                    if(f[k]+f[k-1] > ans)
                        ans = f[k]+f[k-1];
            }
            k++;
            c[k]=a[i];
            f[k]=1;
        }
    }
    if((c[mpos-1]-c[mpos] == 1) || (c[mpos-1]-c[mpos] == -1))
        {
        if(f[mpos]+f[mpos-1] > ans)
            ans = f[mpos]+f[mpos-1];
    }
    else if((c[mpos+1]-c[mpos] == 1) || (c[mpos+1]-c[mpos] == -1))
        {
        if(f[mpos]+f[mpos+1] > ans)
            ans = f[mpos]+f[mpos+1];
    }
    else
        {
        if(f[mpos] > ans)
                ans = f[mpos];
    }
    cout<< ans;
    return 0;
}