import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

H,M,utc = read().split()
H = int(H)
M = int(M)
utc = float(utc[3:])

x = int((utc * 60 + .5) // 1)
T = 60 * H + M - 540 + x

T %= 1440
q,r = divmod(T,60)
print('{:02}:{:02}'.format(q,r))