s, v = input().split()
s, v = int(s), int(v)


t = s//v+10 if s%v==0 else s//v + 1 + 10
if t//60< 8:
    print(f"{7-t//60:0>2}:{60-t%60:0>2}")
elif t//60 == 8:
    print("00:00")    
else:
    k = t - 8*60    
    print(f"{23-k//60:0>2}:{60-k%60:0>2}")