N, M = map(int, input().split())
X = []
for _ in range(M):
    l, r = map(int, input().split())
    X.append((l, r))

X.sort(key = lambda x: x[1])
ans = 0
ma = -1
for l, r in X:
    if ma >= l: continue
    ans += 1
    ma = r
print(N - ans)