import sys
input = sys.stdin.readline

N, M = map(int, input().split())
LR = [tuple(map(int, input().split())) for _ in range(M)]
LR.sort(reverse=True)
now = 10**18
ans = N

for L, R in LR:
    if R<now:
        ans -= 1
        now = L

print(ans)