Problem: There is a grid with N rows and N columns of squares. Let (i, j) be the square at the i-th row from the top and the j-th column from the left.

Each of the central (N-2) \times (N-2) squares in the grid has a black stone on it. Each of the 2N - 1 squares on the bottom side and the right side has a white stone on it.

Q queries are given. We ask you to process them in order. There are two kinds of queries. Their input format and description are as follows:

* `1 x`: Place a white stone on (1, x). After that, for each black stone between (1, x) and the first white stone you hit if you go down from (1, x), replace it with a white stone.
* `2 x`: Place a white stone on (x, 1). After that, for each black stone between (x, 1) and the first white stone you hit if you go right from (x, 1), replace it with a white stone.



How many black stones are there on the grid after processing all Q queries?

Constraints

* 3 \leq N \leq 2\times 10^5
* 0 \leq Q \leq \min(2N-4,2\times 10^5)
* 2 \leq x \leq N-1
* Queries are pairwise distinct.

Input

Input is given from Standard Input in the following format:


N Q
Query_1
\vdots
Query_Q


Output

Print how many black stones there are on the grid after processing all Q queries.

Examples

Input

5 5
1 3
2 3
1 4
2 2
1 2


Output

1


Input

200000 0


Output

39999200004


Input

176527 15
1 81279
2 22308
2 133061
1 80744
2 44603
1 170938
2 139754
2 15220
1 172794
1 159290
2 156968
1 56426
2 77429
1 97459
2 71282


Output

31159505795

Solution (in PYTHON3):

Solution:
import sys
input = sys.stdin.readline

N,Q=map(int,input().split())

seg_el=1<<((N+1).bit_length()) # Segment treeの台の要素数

SEG=[N-2]*(2*seg_el) # 1-indexedなので、要素数2*seg_el.Segment treeの初期値で初期化
SEG2=[N-2]*(2*seg_el)

def getvalue(n,seg_el): # 一点の値を取得
    i=n+seg_el
    ANS=N-2
    
    ANS=min(SEG[i],ANS)
    i>>=1# 子ノードへ
    
    while i!=0:
        ANS=min(SEG[i],ANS)
        i>>=1

    return ANS

def getvalue2(n,seg_el): # 一点の値を取得
    i=n+seg_el
    ANS=N-2
    
    ANS=min(SEG2[i],ANS)
    i>>=1# 子ノードへ
    
    while i!=0:
        ANS=min(SEG2[i],ANS)
        i>>=1

    return ANS

def updates(l,r,x): # 区間[l,r)のminを更新.
    L=l+seg_el
    R=r+seg_el

    while L<R:
        if L & 1:
            SEG[L]=min(x,SEG[L])
            L+=1

        if R & 1:
            R-=1
            SEG[R]=min(x,SEG[R])
        L>>=1
        R>>=1

def updates2(l,r,x): # 区間[l,r)のminを更新.
    L=l+seg_el
    R=r+seg_el

    while L<R:
        if L & 1:
            SEG2[L]=min(x,SEG2[L])
            L+=1

        if R & 1:
            R-=1
            SEG2[R]=min(x,SEG2[R])
        L>>=1
        R>>=1

ANS=(N-2)*(N-2)

MINX=N
MINY=N

for queries in range(Q):
    t,x=map(int,input().split())

    if t==1:
        v=getvalue(x,seg_el)
        ANS-=v
        updates2(1,MINY,x-2)
        MINX=min(MINX,x)

    else:
        v=getvalue2(x,seg_el)
        ANS-=v
        updates(1,MINX,x-2)
        MINY=min(MINY,x)

print(ANS)