暴力求解TLE了怎么办aaa（只拿了40分）

a = input().split()
l = int(a[0])
m = int(a[1])
num = []
remove = []
for i in range(l+1):
    num.append(i)
for j in range(m):
    b = input().split()
    start = int(b[0])
    end = int(b[1])
    for n in range(end-start+1):
        remove.append(start+n)
    for q in remove:
        if q in num:
            num.remove(q)
    remove = []
print(len(num))