Buggy python submission (verdict: Runtime Error):
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(n) :
    _a, _b = map(int, input().split())
    # paths.add((_a, _b))
    # paths.add((_b, _a))
    
# print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))



Fixed submission:
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(m) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))

Buggy python submission (verdict: Runtime Error):
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(n) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
# print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))



Fixed submission:
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(m) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))

Buggy python submission (verdict: Runtime Error):
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(n) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))



Fixed submission:
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(m) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))

Buggy python submission (verdict: Runtime Error):
from itertools import permutations

n, m = map(int, input().split())
# a, b = [], []
paths = set()

for i in range(n) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all((s, t) in paths for s, t in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))



Fixed submission:
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(m) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))

Buggy python submission (verdict: Runtime Error):
from itertools import permutations

n, m = map(int, input().split())
a, b = [], []

for i in range(n) :
    _a, _b = map(int, input().split())
    a.append(_a)
    b.append(_b)

# create set
paths = set()
for i in range(m) :
    paths.add((a[i], b[i]))
    paths.add((b[i], a[i]))
    
print(sum(all((s, t) in paths for s, t in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))



Fixed submission:
from itertools import permutations

n, m = map(int, input().split())
paths = set()

for i in range(m) :
    _a, _b = map(int, input().split())
    paths.add((_a, _b))
    paths.add((_b, _a))
    
print(sum(all(s in paths for s in zip((1,) + p, p)) for p in permutations(range(2, n + 1))))