#include <bits/stdc++.h>

    using namespace std;

#define N 110

int n, a[N];

int main()
{
    
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) scanf("%d", a + i);
    sort(a + 1, a + n + 1);
    int answ = 1, l = 1, res = 1;
    a[n + 1] = INT_MAX;
    for (int i = 2; i <= n + 1; i++){
        bool only = 0;
        for (int j = i - 1; j >= l; j--)
        if (a[i] - a[j] > 1){
            only = 1;
            break;
        }
        if (!only) answ++;
        else{
            l = i;
            res = max(res, answ);
            answ = 1;
        }
    }
    if (res == 1) res = 0;
    printf("%d", res);
}