#include<stdio.h>
 int main()
 {
 	int i,j,n,k,count,count_max;
 	scanf("%d",&n);
 	int a[n];
 	i=0;
 	while(i<n)
 	{
 		scanf("%d",&a[i]);
		i++; 	
	}
	int b[105]={0};
	i=0;
	while(i<n)
	{
		b[a[i]]++;
		i++;
	}
	count=0,count_max=b[0]+b[1];
	i=1;
	while(i<101)
	{
		count=b[i]+b[i+1];
		if(count>count_max)
		{
			count_max=count;	
		}	
		i++;
	}
	printf("%d",count_max);
	return 0;
 }