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:
class LazySegmentTree:
    def __init__(self, op_X, e_X, mapping, compose, id_M, N, array=None):
        __slots__ = ["op_X","e_X","mapping","compose","id_M","N","log","N0","data","lazy"]
        #  それぞれ Xの演算、単位元、f(x),  f\circ g, Xの恒等変換
        self.e_X = e_X; self.op_X = op_X; self.mapping = mapping; self.compose = compose; self.id_M = id_M
        self.N = N
        self.log = (N-1).bit_length()
        self.N0 = 1<<self.log
        self.data = [e_X]*(2*self.N0)
        self.lazy = [id_M]*self.N0
        if array is not None:
            assert N == len(array)
            self.data[self.N0:self.N0+self.N] = array
            for i in range(self.N0-1,0,-1): self.update(i)

    # 1点更新
    def point_set(self, p, x):
        p += self.N0
        for i in range(self.log, 0,-1):
            self.push(p>>i)
        self.data[p] = x
        for i in range(1, self.log + 1):
            self.update(p>>i)
 
    # 1点取得
    def point_get(self, p):
        p += self.N0
        for i in range(self.log, 0, -1):
            self.push(p>>i)
        return self.data[p]
 
    # 半開区間[L,R)をopでまとめる
    def prod(self, l, r):
        if l == r: return self.e_X
        l += self.N0
        r += self.N0
        for i in range(self.log, 0, -1):
            if (l>>i)<<i != l:
                self.push(l>>i)
            if (r>>i)<<i != r:
                self.push(r>>i)

        sml = smr = self.e_X
        while l < r:
            if l & 1: 
                sml = self.op_X(sml, self.data[l])
                l += 1
            if r & 1:
                r -= 1
                smr = self.op_X(self.data[r], smr)
            l >>= 1
            r >>= 1
        return self.op_X(sml, smr)
 
    # 全体をopでまとめる
    def all_prod(s): return self.data[1]
 
    # 1点作用
    def apply(self, p, f):
        p += self.N0
        for i in range(self.log, 0, -1):
            self.push(p>>i)
        self.data[p] = self.mapping(f, self.data[p])
        for i in range(1, self.log + 1):
            self.update(p>>i)
 
    # 区間作用
    def apply(self, l, r, f):
        if l == r: return
        l += self.N0
        r += self.N0
        for i in range(self.log, 0, -1):
            if (l>>i)<<i != l:
                self.push(l>>i)
            if (r>>i)<<i != r:
                self.push((r-1)>>i)

        l2, r2 = l, r
        while l < r:
            if l & 1: 
                self.all_apply(l, f)
                l += 1
            if r & 1:
                r -= 1
                self.all_apply(r, f)
            l >>= 1
            r >>= 1

        l, r = l2, r2
        for i in range(1, self.log + 1):
            if (l>>i)<<i != l:
                self.update(l>>i)
            if (r>>i)<<i != r:
                self.update((r-1)>>i)
     
    """
    始点 l を固定
    f(x_l*...*x_{r-1}) が True になる最大の r 
    つまり TTTTFFFF となるとき、F となる最小の添え字
    存在しない場合 n が返る
    f(e_M) = True でないと壊れる
    """
    def max_right(self, l, g):
        if l == self.N: return self.N
        l += self.N0
        for i in range(self.log, 0, -1): self.push(l>>i)
        sm = self.e_X
        while True:
            while l&1 == 0:
                l >>= 1
            if not g(self.op_X(sm, self.data[l])):
                while l < self.N0:
                    self.push(l)
                    l *= 2
                    if g(self.op_X(sm, self.data[l])):
                        sm = self.op_X(sm, self.data[l])
                        l += 1
                return l - self.N0
            sm = self.op_X(sm, self.data[l])
            l += 1
            if l&-l == l: break
        return self.N
 
    """
    終点 r を固定
    f(x_l*...*x_{r-1}) が True になる最小の l
    つまり FFFFTTTT となるとき、T となる最小の添え字
    存在しない場合 r が返る
    f(e_M) = True でないと壊れる
    """
    def min_left(self, r, g):
        if r == 0: return 0
        r += self.N0
        for i in range(self.log, 0, -1): self.push((r-1)>>i)
        sm = self.e_X
        while True:
            r -= 1
            while r>1 and r&1:
                r >>= 1
            if not g(self.op_X(self.data[r], sm)):
                while r < self.N0:
                    self.push(r)
                    r = 2*r + 1
                    if g(self.op_X(self.data[r], sm)):
                        sm = self.op_X(self.data[r], sm)
                        r -= 1
                return r + 1 - self.N0
            sm = self.op_X(self.data[r], sm)
            if r&-r == r: break
        return 0
        
    # 以下内部関数
    def update(self, k):
        self.data[k] = self.op_X(self.data[2*k], self.data[2*k+1])
    
    def all_apply(self, k, f):
        self.data[k] = self.mapping(f, self.data[k])
        if k < self.N0:
            self.lazy[k] = self.compose(f, self.lazy[k])

    def push(self, k): #propagate と同じ
        if self.lazy[k] is self.id_M: return
        self.data[2*k  ] = self.mapping(self.lazy[k], self.data[2*k])
        self.data[2*k+1] = self.mapping(self.lazy[k], self.data[2*k+1])
        if 2*k < self.N0:
            self.lazy[2*k]   = self.compose(self.lazy[k], self.lazy[2*k])
            self.lazy[2*k+1] = self.compose(self.lazy[k], self.lazy[2*k+1])
        self.lazy[k] = self.id_M

###################################################################
#
###################################################################

e_X = 0
id_M = 1<<32
def op_X(X,Y):
    return ((((X+Y)>>32)%MOD)<<32) + ((X+Y)&MASK)
def compose(D,C):
    a = C>>32; b = C&MASK
    c = D>>32; d = D&MASK
    return (a*c%MOD<<32) + (c*b + d)%MOD
def mapping(C,X):
    x = X>>32; v = X&MASK
    a = C>>32; b = C&MASK
    return ((x*a + v*b)%MOD<<32) + v


# coding: utf-8
# Your code here!
import sys
readline = sys.stdin.readline
read = sys.stdin.read

n,q = map(int, readline().split())
lr = [list(map(int, readline().split())) for _ in range(q)]

op_X = min
e_X = n-1
mapping = min
compose = min
id_M = n-1

sh = LazySegmentTree(op_X, e_X, mapping, compose, id_M, n, array=[n-1]*(n-1)+[0])
sw = LazySegmentTree(op_X, e_X, mapping, compose, id_M, n, array=[n-1]*(n-1)+[0])


ans = (n-2)**2
for t,x in lr:
    x -= 1
    if t==1:
        #idx = sh.max_right(0, lambda v: v >= x)
        idx = sw.point_get(x)
        sh.apply(1,idx,x)
        ans -= idx-1
        #print(idx,x)
        
    else:
        idx = sh.point_get(x)
        sw.apply(1,idx,x)
        ans -= idx-1
        #print(idx,x)
        #sx.point_set(x,1)

print(ans)