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:
# Modified from https://raw.githubusercontent.com/cheran-senthil/PyRival/master/pyrival/data_structures/LazySegmentTree.py
class LazySegmentTree:
    def __init__(self, data, default=0, func=max):
        """initialize the lazy segment tree with data"""
        self._default = default
        self._func = func

        self._len = len(data)
        self._size = _size = 1 << (self._len - 1).bit_length()
        self._lazy = [0] * (2 * _size)

        self.data = [default] * (2 * _size)
        self.data[_size : _size + self._len] = data
        for i in reversed(range(_size)):
            self.data[i] = func(self.data[i + i], self.data[i + i + 1])

    def __len__(self):
        return self._len

    def _push(self, idx):
        """push query on idx to its children"""
        # Let the children know of the queries
        q, self._lazy[idx] = self._lazy[idx], 0

        self._lazy[2 * idx] = max(self._lazy[2 * idx], q)
        self._lazy[2 * idx + 1] = max(self._lazy[2 * idx + 1], q)
        self.data[2 * idx] = max(self.data[2 * idx], q)
        self.data[2 * idx + 1] = max(self.data[2 * idx + 1], q)

    def _update(self, idx):
        """updates the node idx to know of all queries applied to it via its ancestors"""
        for i in reversed(range(1, idx.bit_length())):
            self._push(idx >> i)

    def _build(self, idx):
        """make the changes to idx be known to its ancestors"""
        idx >>= 1
        while idx:
            self.data[idx] = max(
                self._func(self.data[2 * idx], self.data[2 * idx + 1]), self._lazy[idx]
            )
            idx >>= 1

    def add(self, start, stop, value):
        """lazily add value to [start, stop)"""
        start = start_copy = start + self._size
        stop = stop_copy = stop + self._size
        while start < stop:
            if start & 1:
                self._lazy[start] = max(self._lazy[start], value)
                self.data[start] = max(self.data[start], value)
                start += 1
            if stop & 1:
                stop -= 1
                self._lazy[stop] = max(self._lazy[stop], value)
                self.data[stop] = max(self.data[stop], value)
            start >>= 1
            stop >>= 1

        # Tell all nodes above of the updated area of the updates
        self._build(start_copy)
        self._build(stop_copy - 1)

    def query(self, start, stop, default=0):
        """func of data[start, stop)"""
        start += self._size
        stop += self._size

        # Apply all the lazily stored queries
        self._update(start)
        self._update(stop - 1)

        res = default
        while start < stop:
            if start & 1:
                res = self._func(res, self.data[start])
                start += 1
            if stop & 1:
                stop -= 1
                res = self._func(res, self.data[stop])
            start >>= 1
            stop >>= 1
        return res

    def __repr__(self):
        return "LazySegmentTree({0})".format(self.data)


def solve(N, Q, queries):
    N -= 2
    total = N * N
    rows = LazySegmentTree([0] * (N + 1), 0, max)
    cols = LazySegmentTree([0] * (N + 1), 0, max)
    for t, x in queries:
        assert x >= 2
        x -= 2
        if t == 1:
            c = x
            removed = N - cols.query(c, c + 1)
            assert removed >= 0
            total -= removed
            cols.add(c, c + 1, N)
            if removed:
                rows.add(0, removed, N - c)

        elif t == 2:
            r = x
            removed = N - rows.query(r, r + 1)
            assert removed >= 0
            total -= removed
            rows.add(r, r + 1, N)
            if removed:
                cols.add(0, removed, N - r)
    return total


if False:
    import random

    random.seed(0)
    for _ in range(100):
        print(_)
        N = random.randint(3, 10)
        queries = []
        for i in range(2, N):
            queries.append((1, i))
            queries.append((2, i))

        random.shuffle(queries)
        Q = random.randint(0, min(2 * N - 4, 10))
        queries = queries[:Q]
        print(queries)
        solve(N, len(queries), queries)


N, Q = [int(x) for x in input().split()]
queries = [[int(x) for x in input().split()] for i in range(Q)]

print(solve(N, Q, queries))