///         _______
///        |   |   |
///        |___|___|
///        |   |   |
/*  _______|___|___|____________
   |          ___  |            |       *
   |         |   | |            |     *     \   /
   |         |   | |            |===I*      (^.^)_______/
   |_________|___|_|____________|               |____|
     \____/            \____/                   /    \

*/

/// © Copyright 2001-2016 R.Boss
/// Pls dont hack me
/*
- Sasookey is really cool
- Believe it
*/

/// CODEFORCES PROBLEM A

/// I <3 Academy Plus

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fo(i,n,l) for(int i=1;i<=n;i+=l)
#define fos(i,n,l) for(int i=0;i<n;i+=l)
ifstream in("file.in");
ofstream out("file.out");
bool reality_gold_at_IOI=true;
string GABI = "BOSS";
#define nibab return
#define INF 1000000005
#define LINF 1000000000000000005

///________CODE_STARTS_HERE________\\\

int n,a[105],t,k,l;

int main(){
    ios_base :: sync_with_stdio(0);
    cin >> n;
    for(int i=1;i<=n;i++) cin >> a[i];
    sort(a+1,a+n+1);
    k=1;
    for(int i=2;i<=n;i++){
        if(a[i]==a[i-1]) k++;
        else if(a[i]==a[i-1]+1) t=max(t,k+l),l=k,k=1;
        else t=max(t,k+l),l=0,k=1;
    }
    t=max(t,k+l);
    cout << t;
}