import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
INF = 2 ** 63 - 1
mod = 998244353
n, m = mi()
ab = [li() for _ in range(m)]

ab.sort(key = lambda x: x[1])

now = 1
cnt = 0
for a, b in ab:
    if now <= a:
        now = b
        cnt += 1
print(2 * (n - 1) - cnt)