#pragma GCC optimize("O2")

#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#include<cmath>

#include<queue>

#include<stack>

#include<set>

#include<map>

#include<limits.h>

#include<ctime>

#define N 100001

typedef long long ll;

const int inf=999999999;

const int maxn=2017;

using namespace std;

inline int read()

{

    int f=1,x=0;char ch=getchar();

    while(ch>'9'|ch<'0')

    {

        if(ch=='-')

        f=-1;

        ch=getchar();

    }

    while(ch<='9'&&ch>='0')

    {

        x=(x<<3)+(x<<1)+ch-'0';

        ch=getchar();

    }

    return f*x;

}

typedef map<int,bool> mp;

mp m;

int main()

{

	int n=read();

	for(int i=1;i<=n;i++)

	{int k=read();m[k]=1;}

	cout<<m.size()<<endl;

	for(mp::iterator i=m.begin();i!=m.end();i++)

	cout<<i->first<<endl;

}

#pragma GCC optimize("O2")

#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#include<cmath>

#include<queue>

#include<stack>

#include<set>

#include<map>

#include<limits.h>

#include<ctime>

#define N 100001

typedef long long ll;

const int inf=999999999;

const int maxn=2017;

using namespace std;

inline int read()

{

    int f=1,x=0;char ch=getchar();

    while(ch>'9'|ch<'0')

    {

        if(ch=='-')

        f=-1;

        ch=getchar();

    }

    while(ch<='9'&&ch>='0')

    {

        x=(x<<3)+(x<<1)+ch-'0';

        ch=getchar();

    }

    return f*x;

}

set<int>s;

int main()

{

    int n=read();

    for(int i=1;i<=n;i++)

    {int k=read();s.insert(k);}

    printf("%d",s.size());

    for(set<int>::iterator i=s.begin();i!=s.end();i++)

    cout<<*i<<endl;

}