# joins :: String -> String -> Bool
def joins(a, b):
    return a[-1] == b[0]


print (
    [
        ' '.join([w1, w2, w3, w4])
        for w1 in ['the', 'that', 'a']
        for w2 in ['frog', 'elephant', 'thing']
        for w3 in ['walked', 'treaded', 'grows']
        for w4 in ['slowly', 'quickly']
        if joins(w1, w2) and joins(w2, w3) and joins(w3, w4)
    ]
)