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
import math
from collections import defaultdict, deque, Counter
from copy import deepcopy
from bisect import bisect, bisect_right, bisect_left
from heapq import heapify, heappop, heappush
    
input = sys.stdin.readline
def RD(): return input().rstrip()
def F(): return float(input().rstrip())
def I(): return int(input().rstrip())
def MI(): return map(int, input().split())
def MF(): return map(float,input().split())
def LI(): return list(map(int, input().split()))
def TI(): return tuple(map(int, input().split()))
def LF(): return list(map(float,input().split()))
def Init(H, W, num): return [[num for i in range(W)] for j in range(H)]

class BIT():
    # 作りたい要素数nで初期化, 1-index
    # 使用するインスタンス変数の初期化
    def __init__(self, n):
        self.n = n
        self.bit = [0] * (n+1)

    #bit_indexにxをO(log(n))で加算する
    def add(self,i,x):
        #if(i<=0 or i>n):return iに0以下の数字は代入しない
        while i <= self.n:
            self.bit[i] += x
            i += (i & -i)
    #bit_1 + bit_2 + …  + bit_n をO(log(n))で求める
    def sum(self,i):
        s = 0
        #iに0以下の数字は代入しない。
        while i > 0:
            s+=self.bit[i]
            i -= (i & -i)
        return s
    
    def rangesum(self,i,k):
        return self.sum(k) - self.sum(i)
    #a_1 + a_2 + … + a_i >= x となるような最小のiを求める(a_k >= 0)
    #xが0以下の場合は該当するものなし→0を返す
    def lower_bound(self,x):
        if x <= 0:
            return 0
        else:
            i = 0
            r = 1
            #最大としてありうる区間の長さを取得する
            #n以下の最小の二乗のべき(BITで管理する数列の区間で最大のもの)を求める
            while(r<self.n):
                r=r<<1
            len = r
            while len > 0:
                if(i+len<self.n and self.bit[i+len]<x):
                    x-=self.bit[i+len]
                    i+=len
                len = len >> 1
            return i+1

def main():
    N, Q = MI()
    X, Y = BIT(N), BIT(N)
    xmin = N-2
    ymin = N-2
    X.add(1, N-2)
    X.add(N-1, -(N-2))
    Y.add(1, N-2)
    Y.add(N-1, -(N-2))

    res = (N-2)**2
    for i in range(Q):
        a, b = MI()
        if a == 1:
            x = X.sum(b-1)
            if ymin > b-2:
                temp = Y.sum(1)
                Y.add(1, b-2-temp)
                Y.add(xmin+1, -(b-2-temp))
                ymin = b-2
            res -= x
        else:
            y = Y.sum(b-1)
            if xmin > b-2:
                temp = X.sum(1)
                X.add(1, b-2-temp)
                X.add(ymin+1, -(b-2-temp))
                xmin = b-2
            res -= y
            
    print(res)
    
if __name__ == "__main__":
    main()