a = list(map(int,list(input())))
b = list(map(int,list(input())))
L = []
L2 = []
for i in range(8):
L.extend([a[i],b[i]])
while len(L) >2:
L2 = []
for i in range(1,len(L)):
L2.append((L[i-1]+L[i])%10)
L = L2[:]
print("{}{}".format(L[0],L[1]))