Why this reverse lookup function not working

[Emekadavid]

Please, can someone help me explain why this reverse lookup is not working. If I input any of the values in the dictionary, it says not found. Baffled.

mydict = {'a':2, 'b':4, 'c': 5, 'u':98}
#do reverse lookup
v = input('enter a key >')
def reverse_lookup(d, v):
    for keys in d :
        if d[keys] == v :
            print('found')
            return keys
        else :
            print('not found')
            
print(reverse_lookup(mydict, v))

Thanks