def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    l=[]
    i=1
    j=-1
    x=0
    ans=0
    sum=(k*(k+1))-1
   # print (sum)
    for y in range(k):
      ans+=sum
      sum=sum-2      
    return (ans)

k = int(input())
answer=sumOfGroup(k)
print (answer)