#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main(){
    int n;
    cin >> n;
    vector<int> v(n);
    vector<int> m(100);
    
    for(int a_i = 0;a_i < n;a_i++){
       cin >> v[a_i];
    }
    
    int maxapp2 = 0;
    int curmax = 0;  
    
    sort(v.begin(), v.end());
    set<int> s(v.begin(), v.end());
    vector<int> aa(s.begin(), s.end());
    
    for(int i = 0; i < aa.size()-1; i++){
        if(aa[i+1] - aa[i] == 1) {
            curmax = count(v.begin(), v.end(), aa[i]) + count(v.begin(), v.end(), aa[i+1]);
            if(curmax >= maxapp2)
                maxapp2 = curmax;
        }
    }
    
    for(int i = 0; i < n; i++) {
        m[v[i]]++;
    }
    
    int maxapp = 0;
    int bign = 0;
    for(int i = 0; i < 100; i++) {
        if(maxapp < m[i]) {
            maxapp = m[i];
            bign = i;
        }
    }
    
    int a = 0;
    int b = 0;
    
    a = count(v.begin(), v.end(), bign - 1);
    b = count(v.begin(), v.end(), bign + 1);
    
    if(a < b)
        maxapp += b;
    else
        maxapp += a;
    
    if(maxapp2 > maxapp)
        cout << maxapp2;
    else
        cout << maxapp;
    
    return 0;
}