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# (Mono-mcs 6.8.0.105) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
class Program
{
	static void Main(string[] args)
	{
		string[] str = Console.ReadLine().Split();
		int H = int.Parse(str[0]);
		int W = int.Parse(str[1]);
		int[,]A = new int[H,2];
		for(var i=0;i<H;i++){
			string[] str2 = Console.ReadLine().Split();
			A[i,0] = int.Parse(str2[0])-1;
			A[i,1] = int.Parse(str2[1])-1;
		}
		var list = new List<int>();
		list.Add(0);
		int[,]T = new int[W,3];
		int[,]T2 = new int[W,3];
		T[0,1] = W;
		for(var i=0;i<H;i++){
			var list2 = new List<int>(list);
			list.Clear();
			var k = 999999999;
			for(var j=0;j<list2.Count;j++){
				T2[list2[j],0] = T[list2[j],0];
				T2[list2[j],1] = T[list2[j],1];
				T2[list2[j],2] = T[list2[j],2];
			}
			for(var j=0;j<list2.Count;j++){
				if(T2[list2[j],1]<A[i,0]){
					list.Add(list2[j]);
					T[list2[j],0] = T2[list2[j],0];
					T[list2[j],1] = T2[list2[j],1];
					T[list2[j],2] = T2[list2[j],2] + 1;
				} else if(list2[j]<A[i,0]){
					if(T2[list2[j],1]<=A[i,1]){
						list.Add(list2[j]);
						T[list2[j],0] = T2[list2[j],0];
						T[list2[j],1] = A[i,0] - 1;
						T[list2[j],2] = T2[list2[j],2] + 1;
						if(A[i,1] < W-1){
 							k = Math.Min(k,A[i,1]-T2[list2[j],1]+T2[list2[j],2]+2);
						}
					} else {
						list.Add(list2[j]);
						T[list2[j],0] = T2[list2[j],0];
						T[list2[j],1] = A[i,0] - 1;
						T[list2[j],2] = T2[list2[j],2] + 1;
						if(A[i,1] < W-1){
							list.Add(A[i,1]+1);
							T[A[i,1]+1,0] = A[i,1]+1;
							T[A[i,1]+1,1] = T2[list2[j],1];
							T[A[i,1]+1,2] = T2[list2[j],2] + 1;
						}
					}
				} else if(T2[list2[j],0]<=A[i,1]){
					if(T2[list2[j],1]<=A[i,1]){
                      	if(A[i,1] < W-1){
							k = Math.Min(k,A[i,1]-T2[list2[j],1]+T2[list2[j],2]+2);
                        }
					} else {
						k = Math.Min(k,T2[list2[j],2]+1);
						if(A[i,1] < W-1){
							list.Add(A[i,1]+1);
							T[A[i,1]+1,0] = A[i,1]+1;
							T[A[i,1]+1,1] = T2[list2[j],1];
							T[A[i,1]+1,2] = k;
                        }
						k = 999999999;
					}
				} else {
					list.Add(list2[j]);
					T[list2[j],0] = T2[list2[j],0];
					T[list2[j],1] = T2[list2[j],1];
					T[list2[j],2] = T2[list2[j],2] + 1;
				}
			}
			if(k < 999999999){
				if(A[i,1] < W-1){
					list.Add(A[i,1]+1);
					T[A[i,1]+1,0] = A[i,1]+1;
					T[A[i,1]+1,1] = A[i,1]+1;
					T[A[i,1]+1,2] = k;
				}
            }
			long ans = 999999999;
			for(var j=0;j<list.Count;j++){
				ans = Math.Min(ans,T[list[j],2]);
			}
			if(ans == 999999999){
				ans = -1;
			}
			Console.WriteLine(ans);
		}
	}
}