/*
       _ _              ___ _____ ___   __   
__   _(_) | ____ _ ___ / _ \___  / _ \ / /_  
\ \ / / | |/ / _` / __| | | | / / | | | '_ \ 
 \ V /| |   < (_| \__ \ |_| |/ /| |_| | (_) |
  \_/ |_|_|\_\__,_|___/\___//_/  \___/ \___/ 
                                             
 VIKAS SINGH */
        
#include<bits/stdc++.h>
#define endl "\n"
#define pb push_back
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef std::vector<int> vi;
typedef std::vector<long long> vl;
#define f(a,b,c)                for(int a=b;a<c;a++)
#define s(x)                    scanf("%d",&x);
#define sl(x)                   scanf("%lld",&x);
#define s1d(a,n)                for(int ix=0;ix<n;ix++) cin>>a[ix];
#define p(x)                    printf("%d\n",x);
#define pl(x)                   printf("%lld\n",x);
#define p1d(a,n)                for(int ix=0;ix<n;ix++) printf("%d ",a[ix]); printf("\n");
#define p2d(a,n,m)              for(int ix=0;ix<n;ix++){ for(int jx=0;jx<m;jx++) printf("%d ",a[ix][jx]); printf("\n");}
#define MAX 1000005
#define MOD 1000000007

using namespace std;


int main(){
   // freopen("input.in","r",stdin);
   // freopen("output.out","w",stdout);
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int n;
    cin>>n;
    int a[105]={0};
    for (int i = 0; i < n; ++i)
    {
        int t;
        cin>>t;
        a[t]++;
    }
    int m=0;
    for (int i = 0; i < 104; ++i)
    {
        m = max(m, a[i]+a[i+1]);
    }
    cout<<m;
}