#include <bits/stdc++.h>

using namespace std;

int n, mx;
vector < int > v;
map < int,int > mp;

int main(){
   
    cin >> n;
    v.resize(n+1,0);
    
    for(int i = 1; i <= n; i++){
        cin >> v[i];
        mp[v[i]]++;
    }
    
    for(int i = 1; i <= n; i++){
        mx = max(mx,(mp[v[i]]+mp[v[i]-1]));
        mx = max(mx,(mp[v[i]]+mp[v[i]+1]));
    }
    
    cout << mx;
    
    return 0;
}