#include<cstdio>
#include<algorithm>
#include<cstdlib>
using namespace std;
int n,a[1000],b[1000],max1=-10;
int main()
{
    scanf("%d",&n);
for (int i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
       b[a[i]]++;
    }
for (int i=1;i<=100;i++)
{
    if (b[i]+b[i+1]>max1)
        max1=b[i]+b[i+1];
}
printf("%d",max1);
    return 0;
}