Buggy python submission (verdict: Time Limit Exceeded):
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]

passcard = [i+l[0][0] for i in range(l[0][1] - l[0][0]+1)]
for t in range(n[1]-1):
    passcard = [i for i in passcard if l[t+1][0] <= i <= l[t+1][1]]
    
print(len(passcard))

Fixed submission:
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]
minp = l[0][0]
maxp = l[0][1]
for t in range(n[1]):
    minp = max(minp,l[t][0])
    maxp = min(maxp,l[t][1])
print(max(0,maxp-minp+1))

Buggy python submission (verdict: Time Limit Exceeded):
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]

passcard = []
for c in range(l[0][1] - l[0][0]+1):
    passcard.append(l[0][0]+c)

for tt in range(n[1]):
    t = n[1] - tt -1
    for i in range(len(passcard)):
        if not(l[t][0] <= passcard[i] <= l[t][1]):
            passcard[i] = 0
        else:
            passcard[i] = passcard[i]

    passcard = [i for i in passcard if i!=0]
            
print(len(passcard))

Fixed submission:
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]
minp = l[0][0]
maxp = l[0][1]
for t in range(n[1]):
    minp = max(minp,l[t][0])
    maxp = min(maxp,l[t][1])
print(max(0,maxp-minp+1))

Buggy python submission (verdict: Time Limit Exceeded):
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]

passcard = []
for c in range(l[0][1] - l[0][0]+1):
    passcard.append(l[0][0]+c)

for tt in range(n[1]):
    t = n[1] - tt -1
    for i in range(len(passcard)):
        if not(l[t][0] <= passcard[i] <= l[t][1]):
            passcard[i] = 0
        else:
            passcard[i] = passcard[i]

    passcard = [i for i in passcard if i!=0]
            
out = [i for i in passcard if i!=0]
print(len(out))

Fixed submission:
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]
minp = l[0][0]
maxp = l[0][1]
for t in range(n[1]):
    minp = max(minp,l[t][0])
    maxp = min(maxp,l[t][1])
print(max(0,maxp-minp+1))

Buggy python submission (verdict: Time Limit Exceeded):
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]

passcard = []
for c in range(l[0][1] - l[0][0]+1):
    passcard.append(l[0][0]+c)

for t in range(n[1]):
    for i in range(len(passcard)):
        if not(l[t][0] <= passcard[i] <= l[t][1]):
            passcard[i] = 0
        else:
            passcard[i] = passcard[i]
    passcard = [i for i in passcard if i!=0]
            
out = [i for i in passcard if i!=0]
print(len(out))

Fixed submission:
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]
minp = l[0][0]
maxp = l[0][1]
for t in range(n[1]):
    minp = max(minp,l[t][0])
    maxp = min(maxp,l[t][1])
print(max(0,maxp-minp+1))

Buggy python submission (verdict: Time Limit Exceeded):
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]

passcard = []
for c in range(l[0][1] - l[0][0]+1):
    passcard.append(l[0][0]+c)

#print(passcard)

for t in range(n[1]):
    for i in range(len(passcard)):
        if not(l[t][0] <= passcard[i] <= l[t][1]):
            passcard[i] = 0
            #print(passcard)
        else:
            passcard[i] = passcard[i]
            
out = [i for i in passcard if i!=0]
#print(out)
print(len(out))

Fixed submission:
n = list(map(int,input().split()))
l = [list(map(int,input().split())) for i in range(n[1])]
minp = l[0][0]
maxp = l[0][1]
for t in range(n[1]):
    minp = max(minp,l[t][0])
    maxp = min(maxp,l[t][1])
print(max(0,maxp-minp+1))