#!/usr/bin/env python3
#
#
# Doesn't Support in Python so we have to go with some checks

class Student:

    def __init__(self,n1,n2):
        self.n1 = n1
        self.n2 = n2


    def sum(self,a=None,b=None,c=None):

        if a!=None and b!=None and c !=None:
            s = a + b + c

        elif a!=None and b!=None:
            s = a + b

        else:
            s = a

        return s




s1 = Student(78,90)

print(s1.sum(34,45,34))
print(s1.sum(34,45))
print(s1.sum(34))
