#include <stdio.h>
using namespace std;
#include <algorithm>

#define NMAX 1024
#define VMAX 50010

unsigned int NR[VMAX];

int main()
{
NR[0]=1;
int n,A[NMAX],SOL[NMAX],Sol=0;
int i,j;

freopen("economie.in","r",stdin);
freopen("economie.out","w",stdout);
scanf("%d",&n);

for (i=1;i<=n;i++) scanf("%d",&A[i]);

sort(A+1,A+n);

for (i=1;i<=n;i++)
{
for (j=A[i];j<VMAX-1;j++)
if (NR[j-A[i]]!=0)
NR[j]++;
if (NR[A[i]]==1)
{
Sol++;
SOL[Sol]=A[i];
}

}
printf("%d\n",Sol);
for (i=1;i<=Sol;i++) printf("%d\n",SOL[i]);
return 0;
}