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

int n, cnt[107], tmp, maxn;

int main() {
    scanf("%d ", &n);
    for(int i = 1; i<= n; ++i)
    {
        scanf("%d", &tmp);
        cnt[tmp] ++;
    }
    for(int i = 1; i<= 100; ++i)
    {
        if(cnt[i] + cnt[i+1] > maxn) maxn = cnt[i] + cnt[i+1];
    }
    printf("%d\n", maxn);
    return 0;
}