//Daniel Grzegorzewski
#include <bits/stdc++.h>

#define MP make_pair
#define PB push_back
#define ST first
#define ND second

using namespace std;

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

void init_ios()
{
     ios_base::sync_with_stdio(0);
     cin.tie(0);
}

int n, ile[111], x;

int main()
{
	init_ios();	
	cin >> n;
	while (n--) {
		cin >> x;
		ile[x]++;
	}
	int res = 0;
	for (int i = 1; i < 100; ++i)
		res = max(res, ile[i]+ile[i+1]);
	cout<<res<<"\n";
}