#!/bin/python3

import sys

def sumOfGroup(k):
    
    a=[i for i in range(1,(10**7))if(i%2!=0)]
    if k==1:
        return 1
    else:
        m=(k*(k-1))//2
        n=(k*(k+1))//2
        return sum(a[m:n])

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