#include<bits/stdc++.h>
using namespace std; 
#define ll long long int
#define si set<int>
#define vi vector<int>
#define vii vector<vi>
#define mii map<int,int>
#define umii unordered_map<int,int>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pff pair<double,double>
#define myfor(i,n) for(int i=0;i<n;i++)
#define mxx 100001
#define mmm 20
#define PI  3.141592653589793238463
#define minm -2.59807621135
#define mmod 1000000007
#define M 1000000001
#define IMX INT_MAX
#define IMN INT_MIN
#define pre 1e-10
int main()
{
    //clock_t tstart = clock();
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin>>n;
    int arr[101]={0};
    myfor(i,n)
    {
        int num;
        cin>>num;
        arr[num]++;
    }
    int count=0;
    myfor(i,100)
    {
        count=max(count,arr[i]+arr[i+1]);
    }
    cout<<count;
  //cout<<"\n\nTotal Time Taken : "<<fixed<<(double)(-tstart + clock())/CLOCKS_PER_SEC<<"sec\n\n";
  return 0;
}