Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

def main():
    N, M = map(int, input().split())
    seki = set(list(range(1,N+1)))
    for i in range(M):
        l, r = map(int, stdin.readline().rstrip().split())
        #l, r = map(int, input().split())
        seki &= set(list(range(l, r+1)))

    print(len(seki))

if __name__ == '__main__':
    main()

Fixed submission:
# 解説を見ての解答
from sys import stdin

n, m = map(int, stdin.readline().rstrip().split())
lr = [list(map(int, stdin.readline().rstrip().split())) for i in range(m)]

l, r = lr[0][0], lr[0][1]
for i in range(m):
    l = max(l, lr[i][0])
    r = min(r, lr[i][1])

print(max(0,r-l+1))

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
N, M = map(int, input().split())
seki = set(list(range(1,N+1)))
for i in range(M):
    l, r = map(int, stdin.readline().rstrip().split())
    seki &= set(list(range(l, r+1)))

print(len(seki))

Fixed submission:
# 解説を見ての解答
from sys import stdin

n, m = map(int, stdin.readline().rstrip().split())
lr = [list(map(int, stdin.readline().rstrip().split())) for i in range(m)]

l, r = lr[0][0], lr[0][1]
for i in range(m):
    l = max(l, lr[i][0])
    r = min(r, lr[i][1])

print(max(0,r-l+1))

Buggy python submission (verdict: Time Limit Exceeded):
N, M = map(int, input().split())
seki = set(list(range(1,N+1)))
for i in range(M):
    l, r = map(int, input().split())
    seki &= set(list(range(l, r+1)))
print(len(seki))

Fixed submission:
# 解説を見ての解答
from sys import stdin

n, m = map(int, stdin.readline().rstrip().split())
lr = [list(map(int, stdin.readline().rstrip().split())) for i in range(m)]

l, r = lr[0][0], lr[0][1]
for i in range(m):
    l = max(l, lr[i][0])
    r = min(r, lr[i][1])

print(max(0,r-l+1))

Buggy python submission (verdict: Runtime Error):
N, M = map(int, input().split())

seki = set(list(range(1,N+1)))
for i in range(M):
    l, r = map(int, input().split())
    seki &= set(list(range(l, r+1)))
print(len(seki))

Fixed submission:
# 解説を見ての解答
from sys import stdin

n, m = map(int, stdin.readline().rstrip().split())
lr = [list(map(int, stdin.readline().rstrip().split())) for i in range(m)]

l, r = lr[0][0], lr[0][1]
for i in range(m):
    l = max(l, lr[i][0])
    r = min(r, lr[i][1])

print(max(0,r-l+1))

Buggy python submission (verdict: Time Limit Exceeded):
N, M = map(int, input().split())

seki = set(list(range(1,N+1)))
for i in range(M):
    l, r = map(int, input().split())
    seki &= set(list(range(l, r+1)))
print(len(seki))

Fixed submission:
# 解説を見ての解答
from sys import stdin

n, m = map(int, stdin.readline().rstrip().split())
lr = [list(map(int, stdin.readline().rstrip().split())) for i in range(m)]

l, r = lr[0][0], lr[0][1]
for i in range(m):
    l = max(l, lr[i][0])
    r = min(r, lr[i][1])

print(max(0,r-l+1))

Buggy python submission (verdict: Time Limit Exceeded):
N, M = map(int, input().split())
LR = [list(map(int, input().split())) for i in range(M)]

seki = set(list(range(LR[0][0],LR[0][1]+1)))
for i in range(M):
    seki &= set(list(range(LR[i][0], LR[i][1]+1)))

print(len(seki))

Fixed submission:
# 解説を見ての解答
from sys import stdin

n, m = map(int, stdin.readline().rstrip().split())
lr = [list(map(int, stdin.readline().rstrip().split())) for i in range(m)]

l, r = lr[0][0], lr[0][1]
for i in range(m):
    l = max(l, lr[i][0])
    r = min(r, lr[i][1])

print(max(0,r-l+1))