Problem:
Score : 600 points

Problem Statement

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.

Constraints

1 \leq H,W \leq 2\times 10^5

1 \leq A_i \leq B_i \leq W

Input

Input is given from Standard Input in the following format:

H W
A_1 B_1
A_2 B_2
:
A_H B_H

Output

Print H lines. The i-th line should contain the answer for the case k=i.

Sample Input 1

4 4
2 4
1 1
2 3
2 4

Sample Output 1

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.

Solution in C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<iostream>
using namespace std;

const int sz = 2e5 + 1;
typedef pair<int, int>pii;
pii b[sz];

int main()
{
	ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
	int H, W;
	cin >> H >> W;
	for (int i = 0; i < H; i++) {
		cin >> b[i].first >> b[i].second;
	}

	int cur = 1, res = 0;
	for (int i = 0; i < H; i++) {
		++res;

		if (b[i].first <= cur && cur <= b[i].second) {
			res += b[i].second - cur + 1;
			cur = b[i].second + 1;
		}

		if (cur > W) cout << "-1\n";
		else cout << res << '\n';
	}
}