# Closest Key

1
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Given a dictionary with keys of letters and values of a list of letters, write a function closest_key to find the key with the input value closest to the beginning of the list.

Example:

Input:

dictionary = {
'a' : ['b','c','e'],
'm' : ['c','e'],
}
input = 'c'


Output:

closest_key(dictionary, input) -> 'm'


$c$ is at distance 1 from $a$ and 0 from $m$. Hence closest key for $c$ is $m$.

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Python 3.9.6