Python 3:

def equalStacks(h1, h2, h3): # Write your code here

h1 = h1[::-1]
h2 = h2[::-1]
h3 = h3[::-1]

h1hite = sum(h1)
h2hite = sum(h2)
h3hite = sum(h3)

while True:

    if h1hite == h2hite and h1hite == h3hite:
        break
    else:
        if h1hite >= h2hite and h1hite >= h3hite:
            x = h1.pop()
            h1hite -= x
        elif h2hite >= h1hite and h2hite >= h3hite:
            x = h2.pop()
            h2hite -= x
        elif h3hite >= h1hite and h3hite >= h2hite:
            x = h3.pop()
            h3hite -= x

return h1hite