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


void solution(const vector<int>& nums)
{
    int max_count = 0;
    
    unordered_map<int,int> table;
    
    for (int n : nums) {
        table[n]++;
    }
    
    for (int n : nums) {
        int count = 0;
        count += table[n-1];
        count += table[n];
        
        max_count = max(count, max_count);
    }
    
    cout << max_count << endl;
}

int main() {
    int numbers;
    cin >> numbers;
    
    vector<int> nums;
    for (int i = 0; i < numbers; ++i) {
        int n;
        cin >> n;
        nums.push_back(n);
    }
    
    solution(nums);
    
    return 0;
}