#include<bits/stdc++.h>
using namespace std;
 
#define sd(a) scanf("%d",&a)
#define ss(a) scanf("%s",&a)
#define sl(a) scanf("%lld",&a)
#define clr(a) memset(a,0,sizeof(a))
#define debug(a) printf("check%d\n",a)
#define F first
#define S second
#define MP make_pair
#define PB push_back
#define ll long long
#define N 110
int freq[N];

int main()
{
	clr(freq);
	int n,a,i;
	sd(n);
	for(i=0;i<n;i++)
	{
		sd(a);
		freq[a]++;
	}
	int ans=0;
	for(i=0;i<=100;i++)
		ans=max(ans,freq[i]+freq[i+1]);
	printf("%d\n",ans);
}