#include <bits/stdc++.h>
using namespace std;
#define sz(v) int(v.size())


int main(){
    int n;
    cin >> n;
    map<int,int> mapper;
    for(int i = 0 ; i < n ; i++){
        int x;
        cin >> x;
        mapper[x]++;
    }
    map<int,int>::iterator it;
    int ans = 0;
    it = mapper.begin() ;
    pair<int,int>prev;
    prev.first = it->first;
    prev.second = it->second;
    it++;
    ans = max(ans , prev.second);
    for(; it!=mapper.end();it++){
        ans = max(ans, it->second);
        if(abs(prev.first - it->first)<=1)
            ans = max(ans,it->second + prev.second);
        prev = {it->first,it->second};
    }
    cout << ans << endl;
}