#include
using namespace std;
int id[10000000];
int main()
{
int n1,n2,n3,temp,max,count;
cin>>n1>>n2>>n3;
n1=n1+n2+n3;
for(int i=0;i<n1;++i)
{
cin>>temp;
id[temp]=id[temp]+1;
if(id[temp]==2)
{
++count;
}
if(temp>max)
{
max=temp;
}
}
cout<<count<<"\n";
for(int i=0;i<=max;++i)
{
if(id[i]>=2)
{
cout<<i<<"\n";
}
}
return 0;
}