PAT 乙级 1026

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# author: a2htray
# create date: 2023/3/9

"""
PAT 乙级 1026
"""

if __name__ == '__main__':
    start_clock, end_clock = map(int, input().split(' '))
    duration = 1.0 * (end_clock - start_clock) / 100

    h = int(duration // 3600)
    m = int(duration % 3600 // 60)
    s = str(duration % 3600 % 60)

    tokens = s.split('.')

    add = 1 if int(tokens[1][0]) >= 5 else 0
    s = int(tokens[0]) + add

    print('%02d:%02d:%02d' % (h, m, s))