#include <iostream>
#include <iomanip>
int main() {
    long long begin, end;
    std::cin >> begin >> end;
    long long elapsed = end - begin;
    long long hours = elapsed / 3600;           
    long long minutes = (elapsed % 3600) / 60;  
    long long seconds = elapsed % 60;
    std::cout << (hours < 10 ? "0" : "") << hours << ":" 
              << std::setw(2) << std::setfill('0') << minutes << ":" 
              << std::setw(2) << std::setfill('0') << seconds << std::endl;

    return 0;
}