#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <map>

using namespace std;

class Five_Year
{
public:
  Five_Year(int y) : year((y/5*5)) {}

  bool operator<(Five_Year const& fy) const
  {
    return year < fy.year;
  }
  
  string interval() const
  {
    return to_string(year) + "-" + to_string(year+4);
  }
  
private:
  int year;
};


class Average
{
public:
  Average() : sum(0), count(0) {}

  Average& operator+=(int x)
  {
    sum += x;
    ++count;
    return *this;
  }
  
  double average() const
  {
    return double(sum)/count;
  }
  
private:
  int sum;
  int count;
};


int main()
{
  string db;
  cout << "Enter movie information file: ";
  cin >> db;
  
  ifstream ifs(db);

  if ( ! ifs )
  {
    cerr << '"' << db << "\" could not be opened." << endl;
    return 1;
  }

  map<Five_Year, Average> m;
  
  string line;
  while ( getline(ifs, line) )
  {
    istringstream iss(line);
    int year;
    int runtime;

    if (iss >> year >> runtime)
      m[year] += runtime;
    else
      cerr << "ERROR: Bad read: " << line << endl;
  }

  cout << setprecision(1) << fixed;
  for ( pair<Five_Year, Average> const& i : m )
  {
    cout << i.first.interval() << " : " << i.second.average() << endl;
  }
  
  return 0;
}