dict1 = {'maths' : 23 , 'science' : 20 , 'history' : 20}
dict2 = {'computer science' : 22}
dict3 = {}
dict3.update(dict1)
dict3.update(dict2)
print('The value of dict3 is %s'%dict3)
dict2.clear()
print('The values of dict2 after clearing is %s'%dict2)
del dict1
val = input('Enter subject to check ')
output = dict3.get(val.lower(),'The subject is not in dictionary')
print(output)