#include <list.h>
typedef list<int>::const_iterator const_iterator;

int sum(const list<int> & l)
{
   ...
}

int main()
{

  int n, s;
  list<int> l;

  cin>> n;
  
  for(int i=0;i<n;i++) 
    {
      cin>>s; l.push_back(s);
    }
  cout <<"Sum: "<<sum(l) << endl;

}