#include <bits/stdc++.h>   using namespace std;   int main() {     string s1, s2;     cin >> s1 >> s2;     int h1 = stoi(s1.substr(0, 2));     int m1 = stoi(s1.substr(3, 2));     int h2 = stoi(s2.substr(0, 2));     int m2 = stoi(s2.substr(3, 2));     int m3 = (m1 + m2) / 2;     int h3 = h1 + h2;     if (h3 % 2 != 0) m3 += 30;     h3 = h3 / 2;     if (m3 >= 60) {       h3++;       m3 -= 60;     }     if (h3 < 10) cout <<  0 ;     cout << h3 <<  : ;     if (m3 < 10) cout <<  0 ;     cout << m3;   }   