Write a program to compute the sum 1 − 2 + 3 − 4 + ··· + 1999 − 2000 .

# initialize the sum to 0

sum = 0


# loop through the numbers from 1 to 2000

for i in range(1, 2001):

  # add or subtract the current number from the sum

  # depending on whether it is odd or even

  if i % 2 == 0:

    sum -= i

  else:

    sum += i


# print the sum

print(sum)

This program first initializes a sum variable to 0. It then loops through the numbers from 1 to 2000 and adds or subtracts the current number from the sum depending on whether it is odd or even. Finally, it prints the sum.

If you run the program, it will compute and print the sum of 1 − 2 + 3 − 4 + ··· + 1999 − 2000. For example, you might see something like:

0

This is the result of the computation.