Buggy python submission (verdict: Time Limit Exceeded):
n, m = list(map(int, input().split()))
lr_list = list()
for _ in range(m):
    lr_list.append(list(map(int, input().split())))

card_list = [i for i in range(1, n + 1)]

max_l = 0
min_r = 1e6

for l, r in lr_list:
    # print(f"{card_list=}")
    # print(f"{max_l=}, {min_r=}")
    if l > max_l or r < min_r:
        max_l = l
        min_r = r
        new_card_list = []
        for card in card_list:
            if card >= max_l and card <= min_r:
                new_card_list.append(card)
        card_list = new_card_list


print(len(card_list))

Fixed submission:
n, m = list(map(int, input().split()))
# lr_list = list()
l_list = list()
r_list = list()
for _ in range(m):
    l, r = list(map(int, input().split()))
    l_list.append(l)
    r_list.append(r)
    # lr_list.append(list(map(int, input().split())))

min_r = min(r_list)
max_l = max(l_list)
if max_l <= min_r:
    print(min_r - max_l + 1)
else:
    print(0)

Buggy python submission (verdict: Time Limit Exceeded):
n, m = list(map(int, input().split()))
lr_list = list()
for _ in range(m):
    lr_list.append(list(map(int, input().split())))

card_list = [i for i in range(1, n + 1)]

for l, r in lr_list:
    new_card_list = []
    for card in card_list:
        if card >= l and card <= r:
            new_card_list.append(card)
    card_list = new_card_list

print(len(card_list))

Fixed submission:
n, m = list(map(int, input().split()))
# lr_list = list()
l_list = list()
r_list = list()
for _ in range(m):
    l, r = list(map(int, input().split()))
    l_list.append(l)
    r_list.append(r)
    # lr_list.append(list(map(int, input().split())))

min_r = min(r_list)
max_l = max(l_list)
if max_l <= min_r:
    print(min_r - max_l + 1)
else:
    print(0)

Buggy python submission (verdict: Time Limit Exceeded):
n, m = list(map(int, input().split()))
lr_list = list()
for _ in range(m):
    lr_list.append(list(map(int, input().split())))

card_list = [i for i in range(1, n + 1)]

for l, r in lr_list:
    new_card_list = []
    for card in card_list:
        if card >= l and card <= r:
            new_card_list.append(card)
    card_list = new_card_list

print(len(card_list))

Fixed submission:
n, m = list(map(int, input().split()))
# lr_list = list()
l_list = list()
r_list = list()
for _ in range(m):
    l, r = list(map(int, input().split()))
    l_list.append(l)
    r_list.append(r)
    # lr_list.append(list(map(int, input().split())))

min_r = min(r_list)
max_l = max(l_list)
if max_l <= min_r:
    print(min_r - max_l + 1)
else:
    print(0)

Buggy python submission (verdict: Time Limit Exceeded):
n, m = list(map(int, input().split()))
lr_list = list()
for _ in range(m):
    lr_list.append(list(map(int, input().split())))

master_card_set = {i for i in range(1, n + 1)}

for l, r in lr_list:
    card_set = {i for i in range(l, r + 1)}
    master_card_set = master_card_set & card_set

print(len(master_card_set))

Fixed submission:
n, m = list(map(int, input().split()))
# lr_list = list()
l_list = list()
r_list = list()
for _ in range(m):
    l, r = list(map(int, input().split()))
    l_list.append(l)
    r_list.append(r)
    # lr_list.append(list(map(int, input().split())))

min_r = min(r_list)
max_l = max(l_list)
if max_l <= min_r:
    print(min_r - max_l + 1)
else:
    print(0)

Buggy python submission (verdict: Time Limit Exceeded):
n, m = list(map(int, input().split()))
lr_list = list()
for _ in range(m):
    lr_list.append(list(map(int, input().split())))

card_list = [i for i in (1, n + 1)]

set_list = list()
for l, r in lr_list:
    set_list.append({i for i in range(l, r + 1)})

u = set.intersection(*set_list)
print(len(u))


Fixed submission:
n, m = list(map(int, input().split()))
# lr_list = list()
l_list = list()
r_list = list()
for _ in range(m):
    l, r = list(map(int, input().split()))
    l_list.append(l)
    r_list.append(r)
    # lr_list.append(list(map(int, input().split())))

min_r = min(r_list)
max_l = max(l_list)
if max_l <= min_r:
    print(min_r - max_l + 1)
else:
    print(0)