# Arup Guha
# 11/18/2012
# Solution to Junior Knights Homework 7A: Sum Even While

def main():

    n = int(input("Enter a positive integer.\n"))

    # Set counter to first even integer.
    i = 2
    total = 0
    
    # Loop through rest and add
    while i <= 2*n:

        total = total + i;
        i = i + 2

    print("The sum of the first ",n," even integers is ",total,".", sep="")

main()