#include <fstream>
#include <cassert>
#include <string>
#include <iomanip>

ifstream in("average.in");

int main () {
  assert(in);
  int n, t, h, m, s;
  double d;
  char c1, c2;

  in >> n >> d;
  while (in >> t) {
    cout << setw(3) << t << ": ";
    int i=n;
    int o=0;
    double total=0;
    while (i--) {
      in >> ws;
      if (in.peek()=='-') {
	string trash;
	getline(in, trash); cout << '-' << endl;
	goto err;
      }
      in >> h >> c1 >> m >> c2 >> s;
      total += (3600 * h + 60 * m + s);
    }
    o = (int)(total / d + 0.5);
    cout << (o / 60) << (o%60<10 ? ":0" : ":") 
	 << (o%60) << " min/km" << endl;    
  err:;
  }  
}