def shu(n):
    r = 0;
    if n == 1:
       r = 1;
    else:
       r = shu(n - 1) + n - 1 
    return r;

n = int(input())
s = 0
for i in range(1, n+1):
    s += shu(i)
print(s)
/**************************************************************
	Problem: 1145
	User: admin
	Language: Python
	Result: Accepted
	Time:90 ms
	Memory:34480 kb
****************************************************************/