Score : 600 points
There is a grid of squares with H+1 horizontal rows and W vertical columns.
You will start at one of the squares in the top row and repeat moving one square right or down. However, for each integer i from 1 through H, you cannot move down from the A_i-th, (A_i + 1)-th, \ldots, B_i-th squares from the left in the i-th row from the top.
For each integer k from 1 through H, find the minimum number of moves needed to reach one of the squares in the (k+1)-th row from the top. (The starting square can be chosen individually for each case.) If, starting from any square in the top row, none of the squares in the (k+1)-th row can be reached, print -1
instead.
Input is given from Standard Input in the following format:
H W A_1 B_1 A_2 B_2 : A_H B_H
Print H lines. The i-th line should contain the answer for the case k=i.
4 4 2 4 1 1 2 3 2 4
1 3 6 -1
Let (i,j) denote the square at the i-th row from the top and j-th column from the left.
For k=1, we need one move such as (1,1) → (2,1).
For k=2, we need three moves such as (1,1) → (2,1) → (2,2) → (3,2).
For k=3, we need six moves such as (1,1) → (2,1) → (2,2) → (3,2) → (3,3) → (3,4) → (4,4).
For k=4, it is impossible to reach any square in the fifth row from the top.