Question

Sum of the series

Write a program to find the sum 

S of the series where S = x - x^3 + x^5 + ....... upto N terms.

Input

The first line of input is an integer 

X. The second line of input is an integer N.

Explanation

If we take 

X value as 2 in the series upto 5 terms.

Then the series is 2 - 23 + 25 - 27 + 29

So, the output should be 

410.

Sample Input 1
2
5
Sample Output 1
410
Sample Input 2
3
2
Sample Output 2
-24

Answer 1

x = int(input())
N = int(input())
S = 0
k = 1
for i in range(N):
	S += k*(x**(2*i+1))
	k *= -1
print(S)