#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n,m=0,b; int a[1001]={0}; cin>>n; while(n--){ cin>>b; a[b]++; if(a[b]==1) m++; }cout<<m<<endl; int i=1; while(a[i]==0) i++; cout<<i; for(i=i+1;i<1001;i++) if(a[i]>0) cout<<" "<<i; cout<<endl; return 0; }