Buggy python submission (verdict: Time Limit Exceeded):
#!usr/bin/env python3
from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007
sys.setrecursionlimit(1000000)

#A
def A():
    return

#B
def B():
    return

#C
def C():
    return

#D
def D():
    n,m = LI()
    a = LIR(m)
    d = [0 for i in range(n+1)]
    a.sort()
    for i in range(m):
        d[a[i][0]] = i
    for i in range(n):
        d[i+1] = max(d[i],d[i+1])
    for i in range(n):
        a.sort(key = lambda x:x[1])
        mi = a[0][1]-1
        l = d[mi]-(m-len(a))
        a.sort(key = lambda x:x[0])
        a = a[l+1:]
        if len(a) == 0:
            print(i+1)
            quit()
#E
def E():
    return

#F
def F():
    return

#G
def G():
    return

#H
def H():
    return

#Solve
if __name__ == "__main__":
    D()


Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007
sys.setrecursionlimit(1000000)

#A
def A():
    return

#B
def B():
    return

#C
def C():
    return

#D
def D():
    n,m = LI()
    a = LIR(m)
    a.sort(key = lambda x:x[1])
    x = 0
    ans = 0
    for i in range(m):
        if a[i][0] >= x:
            x = a[i][1]
            ans += 1
    print(ans)
#E
def E():
    return

#F
def F():
    return

#G
def G():
    return

#H
def H():
    return

#Solve
if __name__ == "__main__":
    D()

Buggy python submission (verdict: Time Limit Exceeded):
#!usr/bin/env python3
from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007
sys.setrecursionlimit(1000000)

#A
def A():
    return

#B
def B():
    return

#C
def C():
    return

#D
def D():
    n,m = LI()
    a = LIR(m)
    for i in range(n):
        a.sort(key = lambda x:x[1])
        mi = a[0][1]
        l = 0
        r = len(a)
        a.sort(key = lambda x:x[0])
        while r-l>1:
            j = (l+r)//2
            if a[j][0] < mi:
                l = j
            else:
                r = j
        a = a[l+1:]
        if len(a) == 0:
            print(i+1)
            quit()
#E
def E():
    return

#F
def F():
    return

#G
def G():
    return

#H
def H():
    return

#Solve
if __name__ == "__main__":
    D()


Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007
sys.setrecursionlimit(1000000)

#A
def A():
    return

#B
def B():
    return

#C
def C():
    return

#D
def D():
    n,m = LI()
    a = LIR(m)
    a.sort(key = lambda x:x[1])
    x = 0
    ans = 0
    for i in range(m):
        if a[i][0] >= x:
            x = a[i][1]
            ans += 1
    print(ans)
#E
def E():
    return

#F
def F():
    return

#G
def G():
    return

#H
def H():
    return

#Solve
if __name__ == "__main__":
    D()