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<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vvll> vvvll;
typedef vector<ld> vld;
typedef vector<string> vstr;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef priority_queue<ll, vector<ll>, greater<ll>> spqll;  // 小さい順に取り出し
typedef priority_queue<ll, vector<ll>, less<ll>> bpqll;     // 大きい順に取り出し

#define REP(i, n) for (ll i = 0; i < (ll)(n); i++)
#define IREP(i, v) for (auto i = (v).begin(); i != (v).end(); ++i)
#define ALL(v) (v).begin(), (v).end()
#define endl "\n"

ll MOD = 1000000007;
ll INF = 1e18;
ld EPS = 1e-9;
ld PI = M_PI;
vll dx = {1, 0, -1, 0, 1, -1, -1, 1};
vll dy = {0, 1, 0, -1, 1, 1, -1, -1};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a;} //最大公約数
ll lcm(ll a, ll b) { return a / gcd(a, b) * b;}     //最小公倍数

void yes(){ cout << "Yes" << endl;}
void no(){ cout << "No" << endl;}

//-----------------------------------------

//-----------------------------------------

int main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);

  ll h, w;
  cin >> h >> w;
  vll a(h);
  vll b(h);
  REP(i,h){
    cin >> a[i] >> b[i];
    a[i]--; b[i]--;
  }

  vll ans(h, -1);
  ll tmp = 0;
  ll i = 0; ll j = 0;

  while(1){
    if(j < a[i] || b[i] < j){
      tmp++;
      ans[i] = tmp;
      i++;
      if(i == h) break;
    }
    else{
      while(j <= b[i]){
        if(i != 0) j++;
        tmp++;
        if(j == w) break;
      }
      if(j == w) break;
    }
  }
  i = 0;
  tmp = 0;
  while(1){
    if(b[i] < w - 1 && i < h){
      tmp++;
      ans[i] = tmp;
      i++;
    }
    else break;
  }
  REP(i,h) cout << ans[i] << endl;


    
    
  return 0;
}