#include <cstdio>
#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
#define ll long long
using namespace std;
	int n,ans;
	int a[110],num[110];
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
int main()
{
	n=read();
	for (int i=1;i<=n;i++)
	{
		a[i]=read();
		num[a[i]]++;
	}
	for (int i=1;i<=98;i++)
		if (num[i]+num[i+1]>ans) ans=num[i]+num[i+1];
	printf("%d",ans);
	return 0;
}