import sys
def N(n):
    return (n+1)*(n+2)*(n+3)/6
for n in sys.stdin:
    n=int(n)
    if n>2000:
        n=4000-n
    if n<1001:
        print N(n)
    else:
        m=n-1000
        print N(n)-(N(2*m)-m-1)/2
exit()