#include <bits/stdc++.h>
using namespace std;

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define Max(x,y,z) max(x,max(y,z))
#define Min(x,y,z) min(x,min(y,z))
#define fr(i,s,e) for(i=s;i<e;i++)
#define rf(i,s,e) for(i=s-1;i>=e;i--)
#define pb push_back
#define mp make_pair

typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<pair<long long,long long> > vpll;
typedef vector<vector<ll>> vvll;

#define PI 3.141592653589793
#define MOD 1000000007

int main()
{
    ll n;
    cin>>n;
    vector<ll> v(n);
    vector<ll> v2(101,0);
    for(ll i=0;i<n;i++)
    {
        cin>>v[i];
        v2[v[i]]++;
    }
    ll max=0;
    for(int i=1;i<100;i++)
    {
        ll temp=v2[i]+v2[i+1];
        if(temp>max)
        {
            max=temp;
        }
    }
    cout<<max;
    return 0;
}