'''
2^15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.

What is the sum of the digits of the number 2^1000?
'''

a = str(2 ** 1000)
sum = 0

for i in range(0,len(a)):
    sum += int(a[i])
print sum