//start of VMFP template version 1.8
#define Shubham using
#define VMFP namespace
#define IITBHU std
//#include<bits/stdc++.h>	//tests
//#include <stdio.h>
#include <utility>	//pairs
#include<iostream>
#include<iomanip>
//#include<string.h>
#include<vector>	//v.size() v.push_back() v.erase(v.begin()+i) v.insert(v.begin()+i, j)
//#include<unordered_map>
#include<map> //map<string,int> map1 map1.size() map1.erase("value1") map<string,int>::iterator it=map1.begin(); if(it!=map1.end()){cout<<it->first<<" "<<it->second;} while(it!=map1.end())++it;
#include<set> //set1.insert() set1.find() set1.size() set<string>::iterator it=set1.begin(); it!=set1.end() it=set1.find(value1) set1.lower_bound(value1+1) cout<<*it<<endl
#include<stack> //empty() size() top() push() pop()
#include<queue> // empty() size() front() back() push() pop()
#include<climits>
#include<limits>
#include<sstream> //stringstream sso
#include<algorithm>     //  s is a string or vector    next_permutation(s.begin(),s,end())   sort(s.begin(),s.end())   reverse(s.begin(),s.end())
#include<fstream>	//ifstream ifile ifile.open("filename.txt") ifile.close() ofstream ofile
#include<string>
#include<math.h>      // sqrt(r), pow(a,b)=a^b

#define large INT_MAX
#define small INT_MIN
#define FOR(a,b) for (int (a)=0;(a)<(b);(a)++)
#define ALL(x) (x).begin(),(x).end()
#define SORT(a,i,j) sort(a+i,a+j+1) // sorting from integar post i to integar post j both inclusive
#define value(x) cerr << "The value of " << #x << " is " << x << endl
#define value2(x,y) cerr<<"value of "<<#x<<" is "<<x<<" and value of "<<#y<<" is "<<y<<endl
#define value3(x,y,z) cerr<<"value of "<<#x<<" is "<<x<<" and value of "<<#y<<" is "<<y<<" and value of "<<#z<<" is "<<z<<endl
#define value4(x,y,z,h) cerr<<"value of "<<#x<<" is "<<x<<" and value of "<<#y<<" is "<<y<<" and value of "<<#z<<" is "<<z<<" and value of "<<#h<<" is "<<h<<endl
#define value5(x,y,z,h,k) cerr<<#x<<"="<<x<<"  "<<#y<<"="<<y<<"  "<<#z<<"="<<z<<"  "<<#h<<"="<<h<<"  "<<#k<<"="<<k<<endl
#define lli long long int
#define line cout<<endl
#define LMFAO cout<<"muahahahhahahahhahahhahahhahaahhaa"<<endl
#define lmfao cout<<"muahahahhahahahhahahhahahhahaahhaa"<<endl
#define vadd(vector,position,value) vector.insert(vector.begin()+position,value)
#define vremove(vector,position) vector.erase(vector.begin()+position)
#define vpush(vector,value) vector.push_back(value)
#define pii pair<int,int>
#define vi vector<int>
#define mod 1000000007LL
#define sfrom(s,i,j) s.substr(i,j-i+1)
#define mp make_pair
#define fi first
#define se second
Shubham VMFP IITBHU;

string chartostring(char c){
    return string(1,c);
}

string doubletostring(int num,int den){
    stringstream sso;
    sso<<setprecision(15)<<(double)num/den;
    string result;
    sso >> result;
    return result;
}
//end of VMFP template version 1.8

int main(){
    //cout.precision(15);
    int n;
    cin>>n;
    int a[100];
    FOR(i,100)a[i]=0;
    FOR(i,n){
        int tmp;
        cin>>tmp;
        a[tmp-1]++;
    }
    int result = 0;
    for(int i = 0; i < 99; i++){
        if(a[i]+a[i+1] > result){
            result = a[i]+a[i+1];
        }
    }
    cout<<result<<endl;
    return 0;
}