//An Emperor Production
//in Association with Assistant Professor MR Ram Kripal Mishra.
//Copyright (C) 2016,2015 CodeGeeks, Inc.,
//B-217 KIT, First Floor, Rooma, Kanpur, INDIA
//Everyone is permitted to copy and distribute verbatim copies
//of this code, but changing it is not allowed.
#include<bits/stdc++.h>
using namespace std;
#define ln pf("\n")
#define I inr()
#define C inc()
#define S ins()
#define sp pf(" ")
#define loop(a,b) for(int i=a;i<b;i++)
#define pool(a,b) for(int i=a;i>=b;i--)
#define pb push_back
#define ppb pop_back()
#define pf printf
#define pi pair<int,int>
#define sf scanf
#define swi switch
#define vec vector
#define veci vector<int>
#define vecs vector<string>
#define MOD 1000000007
typedef long long ll;
typedef string str;
void ins(string &s){getline(cin,s);}
int to_num(string s){return atoi(s.c_str());}
double power(ll x, ll y){double temp;if( y == 0)return 1;temp = power(x, y/2);if (y%2 == 0)return temp*temp;else{if(y > 0)return x*temp*temp;else return (temp*temp)/x;}}
str to_binary(ll n){str S;if(n==1)return "1";else{S+=to_binary(n>>1);S+=(n%2+'0');}return S;}
ll inr(){ll V;cin>>V;return V;}
str ins(){str s;cin>>s;return s;}
char inc(){char c;cin>>c;return c;}


int main()
{

   int n=I;
    veci v;
    int has[1000]={};
    loop(0,n)
        {
        v.pb(I);
        has[v[i]]++;
    }
    int Max=INT_MIN;
    int counter=0;
    
    for(int i=0;i<101;i++)
        {
        Max=max(Max,has[i]+has[i+1]);
        
            
            
    }
   cout<<Max;
    return 0;

    }