Find the sum of 1, negative 2,. 3, negative 4,5, negative 6,7, negative 8.99 and negative 100

Find the sum of 1, negative 2,. 3, negative 4,5, negative 6,7, negative 8.99 and negative 100

Original formula = (1-2) + (3-4) +. + (99-100)
=-1-1-1+...-1
=-50
The sum of two 1 groups is - 1, so the sum is - 50