def myfunc(n):
ls=[]

# we are going to append all the number from n to 2n

# and return their sum

# since 2n is also included, therefore end point of loop must be 2n+1

if n<0:
    for i in range(n,2*n-1,-1):
       ls.append(i)
else:
    for i in range (n,2*n+1):
        ls.append(i)
return sum(ls)