# Program to find sum of series 1+4-9+16-25+.....+N 
 
import math
print("Enter the range of number(Limit):")
n=int(input())
i=2
sum=1
while(i<=n):
    if(i%2==0):
        sum+=pow(i,2)
    else:
        sum-=pow(i,2)
    i+=1
print("The sum of the series = ",sum)