#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <unordered_set>
#include <unordered_map>

int main() 
{
    int size;
    std::cin >> size;
    std::vector<int> numbers(size);   
    std::unordered_set<int> distinctNum(size);
    std::unordered_map<int,int> numCounts(size);
    std::unordered_set<int> checked(size);
    
    for(int i = 0; i < size; i++)
    {
        std::cin >> numbers[i];
        distinctNum.insert(numbers[i]);
        numCounts[numbers[i]] += 1;
    }
    
    int maxCount = 0;
    for(int i = 0; i < size; i++)
    {
        if(checked.find(numbers[i]) == checked.end())
        {
            checked.insert(numbers[i]);
            if(distinctNum.find(numbers[i]-1) != distinctNum.end())
            {
                maxCount = std::max(maxCount,numCounts[numbers[i]]+numCounts[numbers[i]-1]);
            }
            if(distinctNum.find(numbers[i]+1) != distinctNum.end())
            {
                maxCount = std::max(maxCount,numCounts[numbers[i]]+numCounts[numbers[i]+1]);
            }
              
            maxCount = std::max(maxCount,numCounts[numbers[i]]);
        }
    }
    
    std::cout << maxCount;
    
    return 0;
}