#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    t=k*k-(k-1);
    sum=0
    for i in range(k):
        sum+=(t+(i*2))
    return int(sum)
if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)