#include <fstream>
#include <algorithm>
#define N 1001
#define M 50001
using namespace std;

FILE *fin=fopen("economie.in", "r"), *fout=fopen("economie.out", "w");

int a[N], sol[N], b[M];

int main()
{
    int n, i, j, k=0, x;
    fscanf(fin, "%d", &n);
    for(i=1;i<=n;i++)
    {
        fscanf(fin, "%d", &a[i]);
    }
    sort(a+1, a+n+1);
    for(i=1;i<=n;i++)
    {
        if(!b[a[i]])
        {
            sol[++k]=a[i];
            for(j=a[i];j<=M;j++)
            {
                b[j]=1;
            }
        }
    }
    fprintf(fout, "%d\n", k);
    for(i=1;i<=k;i++)
    {
        fprintf(fout, "%d\n", sol[i]);
    }
}