https://www.hackerrank.com/challenges/equal-stacks/problem

equalstacks.py

# https://www.hackerrank.com/challenges/equal-stacks/problem

# You have three stacks of cylinders where each cylinder has the same diameter, but they may 
# vary in height. You can change the height of a stack by removing and discarding its topmost 
# cylinder any number of times.

# Find the maximum possible height of the stacks such that all of the stacks are exactly the  
# same height. This means you must remove zero or more cylinders from the top of zero or more  
# of the three stacks until they're all the same height, then print the height. The removals  
# must be performed in such a way as to maximize the height.

# Note: An empty stack is still a stack.

# INPUT FORMAT: 

# The first line contains three space-separated integers, n1, n2, and n3, describing the   
# respective number of cylinders in stacks 1, 2, and 3. The subsequent lines describe the   
# respective heights of each cylinder in a stack from top to bottom:
#   * The second line contains n1 space-separated integers describing the cylinder heights   
#     in stack 1. The first element is the top of the stack.
#   * The third line contains n2 space-separated integers describing the cylinder heights  
#     in stack 2. The first element is the top of the stack.
#   * The fourth line contains n3 space-separated integers describing the cylinder heights   
#     in stack 3. The first element is the top of the stack.

def cumsum_from_input():
    a = [0]
    tmp = [int(i) for i in input().split()]
    for i in range(len(tmp)):
        a.append(a[-1] + tmp[-i-1])
    return a

input()
s = [cumsum_from_input(), cumsum_from_input(), cumsum_from_input()]

t = False
while True:
    if not t:
        vals = [s[0].pop(), s[1].pop(), s[2].pop()]
    if vals[0] == vals[1] == vals[2]:
        print(vals[0])
        break
    else: 
        loc = vals.index(max(vals))
        vals[loc] = s[loc].pop()
        t = True