#include <map>
#include <set>
#include <deque>
#include <queue>
#include <cmath>
#include <vector>
#include <cstdio>
#include <fstream>
#include <sstream>
#include <iomanip>
#include <string>
#include <assert.h>
#include <iostream>
#include <cstdlib>
#include <fstream>
#include <algorithm>
#include <functional>
#include <memory.h>
#define pb push_back
#define fst first
#define scn second
#define mp make_pair
#define lint long long
#define sc(x) scanf("%d", &x)
#define rep(i,a,b) for(lint i=a; i<b; i++)
#define mn(a,b,c,d) min(a,min(b,min(c,d)))
using namespace std;
int A[101];
int main(){
    int n;
    cin>>n;
    rep(i,0,n){
        int x;
        cin>>x;
        A[x]++;
    }
    int id=-1, mx=-1;
    rep(i,0,99){
        if(A[i]+A[i+1]>mx){
            mx=A[i]+A[i+1];
            id=i;
        }
    }
    cout<<mx<<endl;
}