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


int main() {
    int n;
    map<int, int> M;
    scanf("%d", &n);
    for(int i = 0;i  < n; i++)
        {
        int x;
        scanf("%d", &x);
        if(M.count(x) == 0)
            M[x] = 0;
        M[x]++;
    }
    int ans = 0;
    map<int,int> M2 = M;
    for(auto p : M) {
        ans = max(ans, max(p.second+M2[p.first-1], p.second+M2[p.first+1]));
    }
    printf("%d\n", ans);
    return 0;
}