Project Euler 22, off by 18,609

Project Euler 22, off by 18,609

I'm working on problem 22 of Project Euler:
Using names.txt (right click and 'Save Link/Target As...'), a 46K text
file containing over five-thousand first names, begin by sorting it into
alphabetical order. Then working out the alphabetical value for each name,
multiply this value by its alphabetical position in the list to obtain a
name score.
For example, when the list is sorted into alphabetical order, COLIN, which
is worth 3 + 15 + 12 + 9 + 14 = 53, is the 938th name in the list. So,
COLIN would obtain a score of 938 × 53 = 49714.
What is the total of all the name scores in the file?
My code (below) getst the answer 871179673. The correct answer should be
87119828, which makes me off by about 18k.
def score(name, pos):
score = 0
for letter in name:
if letter == "A": score += 1
elif letter == "B": score += 2
elif letter == "C": score += 3
elif letter == "D": score += 4
elif letter == "E": score += 5
elif letter == "F": score += 6
elif letter == "G": score += 7
elif letter == "H": score += 8
elif letter == "I": score += 9
elif letter == "J": score += 10
elif letter == "K": score += 11
elif letter == "L": score += 12
elif letter == "M": score += 13
elif letter == "N": score += 14
elif letter == "O": score += 15
elif letter == "P": score += 16
elif letter == "Q": score += 17
elif letter == "R": score += 18
elif letter == "S": score += 19
elif letter == "T": score += 20
elif letter == "U": score += 21
elif letter == "V": score += 22
elif letter == "W": score += 23
elif letter == "X": score += 24
elif letter == "Y": score += 25
elif letter == "Z": score += 26
else: score += 0
# end for loop.
return score * pos