#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<algorithm>
#include<bitset>
#include<list>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<cmath>
#include<string>
#include<cstring>
#include<sstream>
#include<climits>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef set<int> si;
typedef map<string, int> msi;

#define S(x) scanf("%d",&x)
#define SD(x) scanf("%lf",&x)
#define SL(x) scanf("%lld",&x)
#define pb(x) push_back(x)
#define mp make_pair
#define F(i, a, b) for (int i = int(a); i < int(b); i++)
#define forit(it, a) for (it = (a).begin(); it != (a).end(); it++)
#define M(x,i) memset(x,i,sizeof(x))

/* -------------------CODE GOES HERE---------------------- */

int main(){

	int n,t; S(n);
	vi a;

	F(i,0,102){
		a.pb(0);
	}

	F(i,0,n){
		S(t);
		a[t]++;
	}

	int ans = 0;

	F(i,0,101){
		ans = max(ans,(a[i] + a[i+1]));
	}

	printf("%d\n", ans);
}