#include <stdio.h>
#include <string.h>


int n,a,answer=0;
int number[110];


int main()
    {
    memset(number,0,sizeof(number));
    scanf("%d",&n);
    for(int i=0;i<n;i++)
        {
        scanf("%d",&a);
        number[a]++;
        }
    for(int i=1;i<100;i++)
        {
        a = number[i]+number[i+1];
        if(a>answer)
            answer = a;
        }
    printf("%d",answer);
    return 0;
    }