#include<bits/stdc++.h>
    #define _ ios_base::sync_with_stdio(0);cin.tie(0);
    #define f(i,n) for(i=0;i<n;i++)
    #define gc getchar_unlocked()
    #define pb push_back
    #define mp make_pair
    #define fi first
    #define se second
    #define memsetint(a,n,val) f(i,n){a[i]=val;}
    #define M 1000000007
    #define N (long long)314159
    using namespace std;
    typedef long long int ll;
    typedef double ld;
    typedef vector<int> vi;

    ll power(ll a,ll b,ll x)
    {
        ll ans=1;
        a=a%x;
        while(b)
        {
            if(b&1) ans=(ans*a)%x;
            b>>=1;
            a=(a*a)%x;
        }
        return ans%x;
    }


    int main()
    {_
        int n,x,i;
        cin>>n;
        int count[100];
        memsetint(count, 100, 0);
        f(i,n)
        {
            cin>>x;
            count[x]++;
        }
        int m=0;
        for(i=1;i<99;i++)
        {
            x=count[i]+count[i+1];
            m=max(x,m);
        }
        cout<<m<<endl;
        return 0;
    }