"""
By starting at the top of the triangle below and 
moving to adjacent numbers on the line below, the 
maximum total from top to bottom is 23.

3
7 4
2 4 6
8 5 9 3

That is, 3 + 7 + 4 + 9 = 23.

Find the maximum total from top to bottom in 
triangle.txt (right click and 'Save Link/Target As...'), 
a 15K text file containing a triangle with one-hundred lines.

NOTE: This is a much more difficult version of Problem 18. 
It is not possible to try every route to solve this problem, 
as there are 299 altogether! If you could check one trillion 
(1012) routes every second it would take over twenty billion 
years to check them all. There is an efficient algorithm to 
solve it. ;o)

"""

sumlist = [0]*200

f = open('triangle.txt', 'r')
for line in f:
	i = 0
	cells = line.split()
	sumlist_prev = sumlist[:]

	for cell in cells:
		#first number
		if i == 0: 
			sumlist[i] = sumlist_prev[i] + int(cell)
		#last number
		elif i == len(cells)-1: 
			sumlist[i] = sumlist_prev[i-1] + int(cell)	
		else:
			sumlist[i] = max(sumlist_prev[i] + int(cell), sumlist_prev[i-1] + int(cell))		
		i += 1

print max(sumlist)
