class SegmentTree(object):
    def __init__(self, A, dot, unit):
        n = 1 << (len(A) - 1).bit_length()
        tree = [unit] * (2 * n)
        for i, v in enumerate(A):
            tree[i + n] = v
        for i in range(n - 1, 0, -1):
            tree[i] = dot(tree[i << 1], tree[i << 1 | 1])
        self._n = n
        self._tree = tree
        self._dot = dot
        self._unit = unit

    def __getitem__(self, i):
        return self._tree[i + self._n]

    def update(self, i, v):
        i += self._n
        self._tree[i] = v
        while i != 1:
            i >>= 1
            self._tree[i] = self._dot(self._tree[i << 1], self._tree[i << 1 | 1])

    def add(self, i, v):
        self.update(i, self[i] + v)

    def sum(self, l, r): #これで[l,r)から取り出す。
        l += self._n
        r += self._n
        l_val = r_val = self._unit
        while l < r:
            if l & 1:
                l_val = self._dot(l_val, self._tree[l])
                l += 1
            if r & 1:
                r -= 1
                r_val = self._dot(self._tree[r], r_val)
            l >>= 1
            r >>= 1
        return self._dot(l_val, r_val)

def segfunc(x,y):
    return x*y

def main():
    N,M = map(int,input().split())
    Z = []
    for _ in range(M):
        l,r = map(int,input().split())
        l-=1;r-=1 #0-index
        Z.append((l,r))
    Z.sort(key = lambda x: x[1])
    A = [1]*N
    Tree = SegmentTree(A,segfunc,1)
    for i in range(M):
        l,r = Z[i]
        if Tree.sum(l,r+1) == 1:
            Tree.update(r,0)
    ans = 0
    for i in range(N):
        ans += Tree.__getitem__(i)
    print(ans)


if __name__ == '__main__':
    main()