Most water between two walls

heights lists the heights of vertical walls at positions 0, 1, 2, and so on. Pick two walls; the water they could hold between them is the distance between them times the shorter wall's height. Find the most water any pair can hold. Start with the two outermost walls. Moving inward makes the pair narrower, so a narrower pair can only hold more if its shorter wall is taller than the current shorter wall. Keeping the current shorter wall can never help, so move that wall's position inward and try again. Stop when the positions meet.

Write most_water(heights) for a list with at least two walls.

most_water([1, 8, 6, 2, 5, 4, 8, 3, 7])  ->  49
most_water([1, 1])                       ->  1

def most_water(heights):
    ...