class Time60(object):
    def __init__(self,hr,min):
        self.hr = hr
        self.min = min
    def __str__(self):
        return "%d:%d" %(self.hr,self.min)
    __repr__ = __str__
    
    def __add__(self,other):
        return self.__class__(self.hr + other.hr,self.min+other.min)
    def __iadd__(self,other):
        self.hr += other.hr
        self.min += other.min
        return self