#include <bits/stdc++.h>
using namespace std;
#define sd(x) scanf ("%d",&x)
#define pd(x) printf("%d\n",x)
#define sl(x) scanf ("%lld",&x)
#define pl(x) printf("%lld\n",x)
#define ll long long
#define fr(i,n) for(i=0;i<n;i++)
#define fro(i,n) for(i=1;i<=n;i++)
#define vi vector<int>
#define vl vector<long long >
#define vii vector<pair<int,int> >
#define vll vector<pair<long long,long long > >
#define mp make_pair
#define pb push_back
#define mod 1000000007
#define MAX 1000000

int n,a;
int fr[105];

int main() {

	sd(n);

	memset(fr,0,sizeof fr);

	for(int i=0;i<n;i++){
		sd(a);
		fr[a]++;
	}
	int mx = -1;
	for(int i=1;i<=100;i++){
		if(fr[i]+fr[i-1]>mx)
			mx = fr[i]+fr[i-1];
	}
	cout << mx<<endl;
	
	return 0;
}