#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <map>
using namespace std;


map<long long int,long long int> x;

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