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

int n, x, a[101];

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    cin>>n;
    for(int i=0; i<n; i++)
        cin>>x,
        a[x]++;
    x = 0;
    for(int i=0; i<100; i++)
        x = max(x, a[i]+a[i+1]);
    cout<<x;
    return 0;
}