#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <map>
using namespace std;
#define lli long long int
#define mapit map<lli,lli>::iterator
map<lli,lli> ma;

int main() {
    ma.clear();
    lli n;
    cin>>n;
    for(lli i=0;i<n;i++){
        lli a;
        cin>>a;
        ma[a]++;
    }
    lli max=0;
    mapit ii=ma.begin();
    mapit j=ii;
    for(j++;j!=ma.end();ii++,j++){
        if((j->first-ii->first)<=1){
            if(max<(j->second+ii->second))
                max=j->second+ii->second;
        }
        if(max<ii->second)
            max=ii->second;
    }
        if(max<ii->second)
            max=ii->second;
    cout<<max;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}