#include<bits/stdc++.h>

using namespace std;
#define ll long long
//
#define pb push_back
#define pii pair<int,int>
#define X first
#define Y second
#define mod 1000000007
#define mp make_pair
//#define pi acos(-1.0)
//#define V 202
#define rep(i,a,b) for(int i=a;i<=b;i++)
//#define maxn 100005
//#define MAX_NUMBER_OF_NODES 100005
//#define MAX_ASCII_CODE 26


int Set(int N,int p){return N | (1<<p);}
int reset(int N,int p){return  N & ~(1<<p);}
bool check(int N,int p){return (bool)(N & (1<<p));}

int main()
{
    int n;
    cin>>n;
    int arr[n];
    rep(i,0,n-1)cin>>arr[i];
    sort(arr,arr+n);
    int mx = -1;
    int ind = 0;
    while(ind<n)
    {
        int flag=1;
        int d = ind+1;
        while(d<n and arr[d]-1<=arr[ind])flag++,d++;
        if(mx<flag)mx=flag;
        ind++;
    }
    cout<<mx<<endl;
}