[Python] Repeating each element in a list

I have two lists:

x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
y= [5, 2, 3, 2, 3, 3, 3, 3, 5, 3]


I want to create a new list that contains of multiplies x's first element with the amount of y's first element. That is, I'm looking to produce:

z = [0, 0, 0, 0, 0, 1, 1, 2, 2, 2, 3, 3, ...]


How can I create this list?

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