n = int(input())
count = 0
start = n
if n > 1:   
    baff = start - 2
    if baff > 0:
        count += start * baff + (baff - start)
    start = baff
    baff = start + 1
    count += start * baff + (baff - start)
    start = baff    
    while(baff > 2 and start > 2):
        baff = start - 3
        if baff > 0:
            count += start * baff + (baff - start)
        start = baff
        baff = start + 1
        count += start * baff + (baff - start)
        start = baff
    count += start * n + (n - start)
print(count)