N,M = map(int,input().split())
import heapq
heap = []
for _ in range(M):
    l,r = map(int,input().split())
    heapq.heappush(heap,(r,l))
cnt = 0
cur = -1
while heap:
    r,l = heapq.heappop(heap)
    if l<=cur:
        continue
    cur = r
    cnt += 1
print(N-cnt)