//#pragma comment(linker,"/STACK:16777216") /*16Mb*/
#pragma comment(linker,"/STACK:33554432") /*32Mb*/

#ifdef _MSC_VER
#define _CRT_SECURE_NO_WARNINGS
#endif
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <string>
#include <stack>
#include <cmath>
#include <list>
#include <iomanip>
#include <set>
#include <map>
#include <sstream>
#include <cstdio>
using namespace std;

#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,b,a) for (int i = (b)-1; i >= (a); i--)
#define ITER(it,a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); it++)
#define FILL(a,value) memset(a, value, sizeof(a))

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define MP make_pair
#define PB push_back

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;

const double PI = acos(-1.0);
const int INF = 1000 * 1000 * 1000 + 7;
const LL LINF = INF * (LL) INF;

int val[200];
int n, a;
int ans;

int main()
{
	//freopen("in.txt", "r", stdin);
	//ios::sync_with_stdio(false); cin.tie(0);

	cin >> n;
	FOR (i,0,n)
	{
		cin >> a;
		val[a]++;
	}
	FOR (i,1,111)
		ans = max(ans, val[i] + val[i-1]);
	cout << ans;
	return 0;
}