from operator import div,mod
class F:
   def __init__(self):
        self.f=0
   def __call__(self,x):
        l = int(x[0])+int(x[1])+self.f
        self.f = div(l, 10)
        return mod(l, 10)

import itertools
print map(F(),itertools.izip("4358","7540"))