#include <algorithm>

#include <bitset>

#include <cctype>

#include <cerrno>

#include <clocale>

#include <cmath>

#include <complex>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <ctime>

#include <deque>

#include <exception>

#include <fstream>

#include <functional>

#include <limits>

#include <list>

#include <map>

#include <iomanip>

#include <ios>

#include <iosfwd>

#include <iostream>

#include <istream>

#include <ostream>

#include <queue>

#include <set>

#include <sstream>

#include <stdexcept>

#include <streambuf>

#include <string>

#include <utility>

#include <vector>

#include <cwchar>

#include <cwctype>

#include <stack>

#include <limits.h>

using namespace std;

#define MAXN 1010

struct info

{

        int opt,fir;

} b[MAXN];

int i,n,g,mx;

int a[MAXN],h[MAXN];

inline bool check()

{

        for (i = ; i <= g; i++)

        {

                if (b[i].opt == )

                        return false;

        }

        return true;

}

inline bool IDDFS(int dep,int m)

{

        int i,d,tmp,e;

        if (dep > n)

        {

                if (check())

                        return true;

                else return false;

        }

        if (h[a[dep]] <= ) return IDDFS(dep+,m);

        for (i = ; i <= m; i++)

        {

                if (b[i].opt == )

                {

                        d = a[dep] - b[i].fir;

                        if (d <= b[i].fir) continue;

                        b[i].opt = ;

                        tmp = a[dep];

                        while (tmp <= mx && h[tmp] > )

                        {

                                h[tmp]--;

                                tmp += d;

                        }

                        if (tmp > mx)

                        {

                                if (IDDFS(dep+,m))

                                        return true;

                        }

                        b[i].opt = ;

                        e = tmp - d;

                        tmp = a[dep];

                        while (tmp <= e)

                        {

                                h[tmp]++;

                                tmp += d;

                        }

                }

        }

        if (m >= g) return false;

        if ( * a[dep] >= ) return false;

        m++;

        h[a[dep]]--;

        b[m].opt = ;

        b[m].fir = a[dep];

        if (IDDFS(dep+,m))

                return true;

        h[a[dep]]++;

        return false;

}

int main()

{

        scanf("%d",&n);

        for (i = ; i <= n; i++)

        {

                scanf("%d",&a[i]);

                if (a[i] > mx)

                        mx = a[i];

                h[a[i]]++;

        }

        for (i = ; i <= ; i++)

        {

                g = i;

                if (IDDFS(,))

                        break;

        }

        printf("%d\n",g);

        return ;

}