#include <fstream>
#include <iomanip>
#include <iostream>

using namespace std;

class Time {
  private:
    int h,min,s,sec;
  public:
    Time(): h(0), min(0), s(0) {}
    Time(int x,int y,int z): h(x), min(y), s(z) {}
    ~Time() {}
    void Ivedimas()
    {
      cin >> h >> min >> s;
    }
    void Skaiciavimas()
    {
      sec = (((h*60)+min)*60+s);
    }
    int graz_sekundes()
    {
      return sec;
    }
};
int main() {

int n, h, s, min;
int max = -10000000, maxi = -10;

cin >> n;

Time T[100];

	for (int i = 0; i < n; i++)
	{
    T[i].Ivedimas();
    T[i].Skaiciavimas();
  }
  for(int i = 0; i < n; i++)
  {
    for(int j = 0; j < n; j++)
    {
      maxi = T[i].graz_sekundes() + T[j].graz_sekundes();
      if(maxi >= 86400)
      {
        maxi = maxi-86400;
      }
      if(i!=j && maxi > max)
      {
        max=maxi;
      }
    }
  }

  h = max/3600;
  min = (max-h*3600)/60;
  s = max%60;




    if((h<=9&&min<=9)&&s<=9)
     cout<<"0"<< h << ":"<<"0"<< min << ":"<<"0"<< s << endl;
    if((h<=9&&min<=9)&&s>=10)
     cout<<"0"<< h << ":"<<"0"<< min << ":"<<s << endl;
    if((h<=9&&min>=10)&&s<=9)
     cout<<"0"<<h<<":"<<min<<":"<<"0"<<s<<endl;
    if((h<=9&&min>=10)&&s>=10)
     cout<<"0"<< h << ":"<< min<< ":"<< s << endl;
    if((h>=10&&min>=10)&&s>=10)
     cout<< h << ":"<< min << ":"<< s << endl;
    if((h>=10&&min>=10)&&s<=9)
     cout<< h << ":"<< min<< ":"<<"0"<< s << endl;
    if((h>=10&&min<=9)&&s<=9)
     cout<< h << ":"<<"0"<< min<< ":"<<"0"<< s << endl;
    if((h>=10&&min<=9)&&s>=10)
     cout<< h << ":"<<"0"<< min<< ":"<< s << endl;


return 0;
}