//STARTSOLUTION
#include <iostream>
#include <limits>
#include <fstream>
#include <string>
#include <stack>
#include <algorithm>
#include <cctype>
//ENDSOLUTION
#include <cassert>

using namespace std;

//STARTSOLUTION
bool validate(string const& file_name)
{
    ifstream ifs{file_name};
    string tag{};
    stack<string> xml_stack{};
    bool closed{false};

    while (getline(ifs.ignore(numeric_limits<streamsize>::max(), '<'), tag, '>'))
    {
        
        if (tag.front() == '/')
        {
            tag.erase(0, 1);
            closed = true;
        }

        if (!std::all_of(tag.begin(), tag.end(), [](unsigned char c){ return std::isalpha(c); }))
        {
            cout << "Tag: '" + tag + "' is not correct" << endl;
            return false;
        }
        
        if (closed)
        {
            if (xml_stack.top() == tag)
            {
                xml_stack.pop();
                closed = false;
            }
            else
            {
                cout << "Tag: '" + tag + "' not closed" << endl;
                return false;
            }
        }
        else
        {
            xml_stack.push(tag);
        }
    }
    if (!xml_stack.empty())
    {
        cout << "There are unclosed tags" << endl;
        return false;
    }
    cout << "No syntax errors" << endl;
    return true;
    
}
//ENDSOLUTION

int main()
{
    assert( validate("correct.xml") );            //Funktionen ska returnera true
    assert( !validate("incorrect_tag.xml") );     //Funktionen ska returnera false
    assert( !validate("not_closed_nested.xml") ); //Funktionen ska returnera false
    assert( !validate("tag_not_closed.xml") );    //Funktionen ska returnera false
}