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

int n;
int cc[1000 + 10];

int main() {
    cin >> n;
    for(int i = 0; i < n; i++) {
        int a; cin >> a;
        cc[a]++;
    }
    int mx = 0;
    for(int v = 1; v <= 100; v++) {
        mx = max(mx, cc[v] + cc[v+1]);
    }
    cout << mx << endl;
    return 0;
}