Find out the biggest number in a int list

#include <iostream>
#include <list>
#include <iterator>
using namespace std;

int max(list<int> a_list)
{
    cout << "You gave me a list with a length of " << a_list.size() << "." << endl;
    a_list.sort();
    a_list.reverse();

    auto iterator = a_list.begin(); //create a iterator
    advance(iterator, 0); //give a 0 index, get the expected value in that list
    cout << *iterator << " is the biggest in this list." << endl; //from pointer address get int value
 
    return *iterator;
}

int main ()
{
    //std::list<int> mylist;
    //list included in std namespace.
    list<int> mylist={2, 3, 4, 1, 0}; //define a list contains int value
    max(mylist); //call max function
    return 0;
}