#include<bits/stdc++.h>
#define mp make_pair
#define PII pair<int,int>
#define fi first
#define se second
#define pb push_back
#define ll long long
#define ull unsigned long long
#define ui unsigned int
#define sci(x) scanf("%d",&x)
#define scs(s) scanf("%s",s)
#define scc(c) scanf("%c",c)
#define scd(d) scanf("%lf",&d)
#define scld(ld) scanf("%Lf",&ld)
using namespace std;

//********************************************
//Error tracking
#define show(args...) { vector<string> _v = split(#args, ','); err(_v.begin(), args); }

vector<string> split(const string& s, char c) {
    vector<string> v;
    stringstream ss(s);
    string x;
    while (getline(ss, x, c))
        v.emplace_back(x);
    return move(v);
}

void err(vector<string>::iterator it) {}
template<typename T, typename... Args>
void err(vector<string>::iterator it, T a, Args... args) {
    cerr << it -> substr((*it)[0] == ' ', it -> length()) << " = " << a << '\n';
    err(++it, args...);
}
//********************************************

const int NMAX = 105;

int n,a[NMAX],fr[NMAX];

int main()
{
    int i;

   // freopen("input","r",stdin);
   // freopen("output","w",stdout);
    cin.sync_with_stdio(false);

    cin >> n;
    for (i = 1; i <= n; i++) 
    {
        cin >> a[i];
        fr[a[i]]++;
    }

    int mx = 0;
    for (i = 0; i <= 100; i++) mx = max(mx, fr[i] + fr[i + 1]);

    cout << mx << "\n";
    return 0;   
}