#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

#define s(x) scanf("%lld", &(x))
#define ss(x) scanf("%d", &(x))

struct node{
    int x, y;
};

int main()
{
    int n, mx = 0;
    cin >> n;
    map< int, int> mp;
    map< int, int>:: iterator it;

    for(int i=0; i<n; i++){
        int a;
        cin >> a;
        mp[a]++;
    }

    vector< node > ve;
    node get;

    for( it = mp.begin(); it != mp.end(); it++ ){

        int b = it->second;
        mx = max(mx, b);
        get.x = it->first;
        get.y = b;
        ve.push_back(get);
    }

    int len = ve.size();

    for( int i=0; i<len-1; i++){
        int dif = abs( ve[i+1].x - ve[i].x );
        if( dif <= 1)
            mx = max ( mx, ve[i+1].y + ve[i].y);
    }

    cout << mx << "\n";

    return 0;
}