#include <bits/stdc++.h>
using namespace std;

#define md 1000000007
long long mulMod(long long x, long long y, long long p);
int pector(long long a, long long s, long long d, long long n) ;

long long powMod(long long x, long long k, long long m) {
	if (k == 0) return 1;
	if ((k & 1)) return mulMod(x, powMod(x, k - 1, m), m);
	else return powMod(mulMod(x, x, m), k / 2, m);
}
long long mulMod(long long x, long long y, long long p) {
	if (y == 0) return 0;
	if (x < 1000111000111000111LL / y) return x * y % p;
	long long mid = mulMod((x + x) % p, y >> 1LL, p);
	if (y & 1) return (mid + x) % p;
	else return mid;
}
int pector(long long a, long long s, long long d, long long n) 
{
	long long x = powMod(a, d, n);
	if (x == 1) return 1;
	for (int r = 0; r < s; ++r) {
		if (x == n - 1) return 1;
		x = mulMod(x, x, n);
	}
	return 0;
}


int haiprime(long long n) 
{
	if (n <= 1 || (n > 2 && n % 2 == 0)) return 0;
	long long test[] = { 2,3,5,7,11,13,17,19,23,-1 };
	long long d = n - 1, s = 0;
	while (d % 2 == 0) ++s, d /= 2;
	for (int i = 0; test[i] < n && test[i] != -1; ++i)
		if (!pector(test[i], s, d, n)) return 0;
	return 1;
}

int main()
{
	
	long long t, n;
	int i;
	cin >> n;
	int arr[1005] = {0};
	for (i = 0; i < n; ++i)
	{
		cin >> t;
		arr[t] += 1;
	}
	int cnt = 0;
	for (i = 0; i < 101; ++i)
	{
		cnt = max(cnt, arr[i + 1] + arr[i]);
	}
	cout << cnt;
}