### BUGGY CODE ###

import sys,heapq
input = sys.stdin.buffer.readline

h,w = map(int,input().split())


#dp[i] : iの時の最小右移動回数
dp = [0]*(w+1)

#解候補
res = [0]*w

#解候補から消されるもの
anti = []



#Ai = {1:dp[i]はvalid 0:invalid}

#A1 ... AnのBIT(1-indexed)
BIT = [0]*(w+100)

#A1 ~ Aiまでの和 O(logN)
def BIT_query(idx):
    res_sum = 0
    while idx > 0:
        res_sum += BIT[idx]
        idx -= idx&(-idx)
    return res_sum

#Ai += x O(logN)
def BIT_update(idx,x):
    while idx <= w:
        BIT[idx] += x
        idx += idx&(-idx)
    return

for i in range(1,w+1):
    BIT_update(i,1)
flag = False

for i in range(1,h+1):
    a,b = map(int,input().split())
    if flag:
        print(-1)
        continue
    #a-1,b+1の値を計算
    for x in [a-1,b+1]:
        #端で操作不可能
        if x in (0,w+1):
            continue

        #validな値の場合そのまま下に行く
        if dp[x] != -1:
            continue
        
        #x以下のvalidな個数
        k = BIT_query(x-1)

        #k番目のvalidな位置okからXに行く
        if k == 0:
            continue
        ok = x
        ng = 0
        while ok-ng > 1:
            mid = (ok+ng)//2
            if BIT_query(mid) == k:
                ok = mid
            else:
                ng = mid
        #xをvalidにする
        dp[x] = dp[ok] + (x-ok)
        BIT_update(x,1)
        heapq.heappush(res,dp[x])

    k = BIT_query(a-1)+1

    while True:
        ng = 0
        ok = w
        while ok-ng > 1:
            mid = (ok+ng)//2
            if BIT_query(mid) >= k:
                ok = mid
            else:
                ng = mid

        if ok > b or dp[ok] == -1:
            break
        
        heapq.heappush(anti,dp[ok])
        dp[ok] = -1
        BIT_update(ok,-1)
    
    while anti and anti[0] == res[0]:
        heapq.heappop(anti)
        heapq.heappop(res)

    if res:
        print(res[0]+i)
    else:
        flag = True
        print(-1)


### FIXED CODE ###

import sys,heapq
input = sys.stdin.buffer.readline


def main():
    h,w = map(int,input().split())

    #dp[i] : iの時の最小右移動回数
    dp = [0]*(w+1)

    #解候補
    res = [0]*w

    #解候補から消されるもの
    anti = []


    #Ai = {1:dp[i]はvalid 0:invalid}

    #A1 ... AnのBIT(1-indexed)
    BIT = [0]*(w+1)

    #A1 ~ Aiまでの和 O(logN)
    def BIT_query(idx):
        res_sum = 0
        while idx > 0:
            res_sum += BIT[idx]
            idx -= idx&(-idx)
        return res_sum

    #Ai += x O(logN)
    def BIT_update(idx,x):
        while idx <= w:
            BIT[idx] += x
            idx += idx&(-idx)

    for i in range(1,w+1):
        BIT_update(i,1)

    for i in range(1,h+1):
        a,b = map(int,input().split())
        
        #a-1,b+1の値を計算
        x = a-1
        if x != 0 and x != w+1 and dp[x] == -1:
            #x以下のvalidな個数
            k = BIT_query(x-1)

            #k番目のvalidな位置okからXに行く
            if k != 0:
                ok = x
                ng = 0
                while ok-ng > 1:
                    mid = (ok+ng)//2
                    if BIT_query(mid) == k:
                        ok = mid
                    else:
                        ng = mid
                #xをvalidにする
                dp[x] = dp[ok] + (x-ok)
                BIT_update(x,1)
                heapq.heappush(res,dp[x])
                
        x = b+1
        if x != 0 and x != w+1 and dp[x] == -1:
            #x以下のvalidな個数
            k = BIT_query(x-1)

            #k番目のvalidな位置okからXに行く
            if k != 0:
                ok = x
                ng = 0
                while ok-ng > 1:
                    mid = (ok+ng)//2
                    if BIT_query(mid) == k:
                        ok = mid
                    else:
                        ng = mid
                #xをvalidにする
                dp[x] = dp[ok] + (x-ok)
                BIT_update(x,1)
                heapq.heappush(res,dp[x])

        k = BIT_query(a-1)+1

        while True:
            ng = a-1
            ok = b+1
            while ok-ng > 1:
                mid = (ok+ng)//2
                if BIT_query(mid) >= k:
                    ok = mid
                else:
                    ng = mid

            if ok > b or dp[ok] == -1:
                break
            
            heapq.heappush(anti,dp[ok])
            dp[ok] = -1
            BIT_update(ok,-1)
        
        while anti and res and anti[0] == res[0]:
            heapq.heappop(anti)
            heapq.heappop(res)

        if res:
            print(res[0]+i)
        else:
            print(-1)

if __name__ == '__main__':
    main()