n - {1 - [n - (1 - n) - 1]} first you do - (1 - n) [multiply -1 to 1 - n)
n - {1 - [n - 1 + n - 1]}
n - {1 - [n + n - 1 - 1]}
n - {1 - [2n - 2]} you do - (2n - 2) [multiply -1 to 2n - 2)
n - {1 -2n + 2}
n - {-2n + 3} you do - (-2n + 3) [multiply -1 to -2n + 3)
n + 2n - 3
3n - 3
answer
