# summing up all numbers from 0 to N, using a while loop
# note: in my opinion, a for loop is more simple, but the goal
# of this example is to show that for loops can always be replaced
# by while loops

# get N from the user
N_string = raw_input("please enter N: ")
N = int(N_string)

# compute the sum
total = 0
i = 0
while i <= N:
    total = total + i
    i = i+1

# print the result
print "total =", total