import sys


def sumOfGroup(k):
    odd_number=-1
    start=1
    empty_list=[]
    while True:
        for i in range(0,start):
            odd_number+=2
            empty_list.append(odd_number)
            if len(empty_list)==k:
                total=0
                for j in empty_list:
                    total+=j
                return total
        start+=1
        empty_list.clear()





    # Return the sum of the elements of the k'th group.

if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)