#include <cstdio>
#include <algorithm>

using namespace std;

int n, a[1010];

int main()
{
    int z = 0;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
    for (int i = 1; i <= 100; i++)
    {
        int s = 0;
        for (int j = 1; j <= n; j++) if (a[j] == i || a[j] == i + 1) s++;
        z = max(z, s);
    }
    printf("%d", z);
    return 0;
}