#include <iostream>
#include <cmath>
#include <map>
#include <limits.h>
#define X first 
#define Y second 
#define MP make_pair
#define PB push_back
#define ll long long
#define CLR(x) memset(x,0,sizeof(x))
#define vrep(i, v)    for(int i = 0; i < v.size(); i++)
#define rep(i, a, b)  for(int i = a; i <= b; i++)
#define drep(i, a, b) for(int i = a; i >= b; i--)
using namespace std;
const double pi = acos(-1.), eps = 1e-6;
const int                   Maxn=200010,Maxm=2500000,Mo=1e9 + 7,oo=INT_MAX >> 1;
const int sp[4][2] = {{-1,0},{0,1},{1,0},{0,-1}};
int T;
using namespace std;
ll a[Maxn],b[Maxn];
ll n,m,s;
ll f[1010][1010],C[1010][1010];
bool vis[Maxn];
int x[Maxn],y[Maxn];
map<int,int> sum;
int main()
{
	cin >> n;
	rep(i,1,n) {
		cin >> a[i];
		sum[a[i]] ++;
	}
	int ans = 0;
	for (int i = 1;i<100;i++){
		ans = max(ans, sum[i-1] + sum[i]);
	}
	cout << ans <<  endl;
    return 0;
}