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



int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    int *c = (int *)calloc(sizeof(int), (201));
    long long n;
    scanf("%lld", &n);
    long long i, a[n];
    for(i = 0; i < n; i++){
        scanf("%lld", &a[i]);
        c[a[i]]++;
    }
    long long max = 0;
    for(i = 0; i < 101; i++){
        long long difference = c[i] + c[i + 1];
        if (difference > max) max = difference;
    }
    printf("%lld\n", max);
    return 0;
}