//arafat islam, 1507017, cse, KUET.
//aiproshar
#define LL              long long
#define UL              unsigned long long
#define PI              acos(-1.0)
#define Di(x)           int x;scanf("%d",&x)
#define Si(x)           scanf("%d",&x);
#define So(x)           printf("%d",x)
#define vout(x)         for(int i = 0 ; i < x.size(); i++)cout<<x[i]<<" "
#define pb              push_back
#define IO              ios_base::sync_with_stdio(0);cin.tie(0)
#define READ            freopen("C:/Users/arafat_islam/Desktop/in.txt","r",stdin)
#define WRITE           freopen("C:/Users/arafat_islam/Desktop/out.txt","w",stdout)
#define NL              printf("\n")
//----------------------------------------------------------------------------------------
#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    map<int,int>mp1;
    for( int i = 0 ; i < n ; i++)
    {
        int temp;
        cin>>temp;
        mp1[temp]++;
    }
    int max = 0;
    int ans = 0;
    map<int , int > m1;
    int temp = 0;
    for(int i = 0 ; i < 100 - 1 ; i++)
    {
        if( mp1[i] + mp1[i+1] > temp)
        {
            temp = mp1[i] + mp1[i+1];
        }
    }
    cout<<temp;
    return 0;
}