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

typedef long long int lld;
typedef long double ldb;

#define f first
#define s second
#define mp make_pair
#define pb push_back

// in the name of god
int f[2010];
int main(){
	int n;
	cin >> n;
	int x;
	for(int i = 0; i < n; i++){
		cin >> x;
		f[x]++; f[x+1]++;
	}
	int mx = 0;
	for(int i = 0; i <=100; i++) mx = max(mx, f[i]);
	cout << mx << endl;
}