#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n1,n2,n3, i,input, c;
    cin>>n1>>n2>>n3;
    vector<int>N1,N2,N3,N4;
    for(i =0;i<n1;i++)
    {
        cin>>input;
        N1.push_back(input);
    }
    for(i =0;i<n2;i++)
    {
        cin>>input;
        N2.push_back(input);
    }
    for(i =0;i<n3;i++)
    {
        cin>>input;
        N3.push_back(input);
    }
    sort( N1.begin(), N1.end() );
    N1.erase( unique(N1.begin(), N1.end() ), N1.end() );
    sort( N2.begin(), N2.end() );
    N2.erase( unique( N2.begin(),N2.end() ), N2.end() );
    sort( N3.begin(), N3.end() );
    N3.erase( unique( N3.begin(), N3.end() ), N3.end() );
    copy( N1.begin(), N1.end(), back_inserter(N3));
    copy( N2.begin(), N2.end(), back_inserter(N3));
    sort( N3.begin(), N3.end() );
    for (auto i = N3.begin(); i != N3.end(); ++i)
    {
        int c = count(N3.begin(), N3.end(), *i);
        if(c>=2)
        N4.push_back(*i);
    }
    N4.erase( unique(N4.begin(), N4.end() ), N4.end() );
    cout<< N4.size()<<'\n';
    for (auto i = N4.begin(); i != N4.end(); ++i)
    cout << *i <<'\n';


}

Line 23: error: bits/stdc++.h: No such file or directory
In function 'int main()':
Line 32: error: ISO C++ forbids declaration of 'i' with no type
compilation terminated due to -Wfatal-errors.