N,M = map(int,input().split())
A = sorted([list(map(int,input().split())) for _ in range(M)],key=lambda x:x[1])
cnt = 1
cur = A[0][1]
for i in range(1,M):
    a,b = A[i]
    if a>=cur:
        cur = b
        cnt += 1
print(2*(N-1)-cnt)