PTA乙1026（python3）

def string(s):
    t = str(s)
    if s <= 9:
        t = '0' + str(s)
    return t
c1, c2 = map(int, input().split())
T = (c2 - c1)/100
if (T - int(T)) - 0.5 >= 0:
    T = int(T) + 1
else:
    T = int(T)
s = T % 60
m = int((T - s) / 60) % 60
h = int((T - (m*60) + s) / 3600)
ss = string(s)
mm = string(m)
hh = string(h)
print(hh + ':' + mm + ':' + ss)