import numpy

#askisi 2 apo epanaliptikes erotisis
n = int(input('Please enter the value of n'))
x = int(input('Please enter the value of x'))
sum = 0
if n > 0:
    for i in range(1,n+1):
        sum = sum + x**i
elif n < 0:
    for i in range(1,n+1):
        sum = sum + 1/x**1 #prota ena gini x**1 kai meta ena kami 1 dia x**1
else:
    sum = 1
print('sum = %f' % sum)