/******************************************
*    AUTHOR:         CHIRAG AGARWAL       *
*    INSTITUITION:   BITS PILANI, PILANI  *
******************************************/
#include <bits/stdc++.h>
using namespace std;
 
typedef long long LL; 
typedef long double LD;
int cnt[102];

int main() {

		int n;
		scanf("%d",&n);
		for(int i=0;i<n;i++)
		{
			int a;
			scanf("%d",&a);
			cnt[a]++;
		}
		int ans=0;
		for(int i=1;i<100;i++)
		{
			ans=max(ans,cnt[i]+cnt[i+1]);
		}
		printf("%d",ans );
	return 0;
}