Buggy python submission (verdict: Runtime Error):
import sys;sys.setrecursionlimit(100000);n,k=map(int,input().split());x,t,e,c=10**9+7,[set()for _ in range(n)],enumerate,k
for i in range(n-1):a,b=map(int,input().split());t[a-1].add(b);t[b-1].add(a)
def b(o):
  for i,j in e(t[o-1]):c=(c*(k-2-i))%x;t[j-1].discard(o);b(j)
for i,j in e(t[0]):c=(c*(k-1-i))%x;t[j-1].discard(1);b(j)
print(c)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Buggy python submission (verdict: Runtime Error):
import sys;sys.setrecursionlimit(100000);n,k=map(int,input().split());x,t=10**9+7,[set()for _ in range(n)]
for i in range(n-1):a,b=map(int,input().split());t[a-1].add(b);t[b-1].add(a)
c=k
def b(o):
  for i,j in enumerate(t[o-1]):c=(c*(k-2-i))%x;t[j-1].discard(o);b(j)
for i,j in enumerate(t[0]):c=(c*(k-1-i))%x;t[j-1].discard(1);b(j)
print(c)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Buggy python submission (verdict: Runtime Error):
import sys;sys.setrecursionlimit(100000);n,k=map(int,input().split());x,t=10**9+7,[set()for _ in range(n)]
for i in range(n-1):;a,b=map(int,input().split());t[a-1].add(b);t[b-1].add(a)
c=k
def b(o):
  global c
  for i,j in enumerate(t[o-1]):c=(c*(k-2-i))%x;t[j-1].discard(o);b(j)
for i,j in enumerate(t[0]):c=(c*(k-1-i))%x;t[j-1].discard(1);b(j)
print(c)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Buggy python submission (verdict: Runtime Error):
import sys;sys.setrecursionlimit(100000);n,k=map(int,input().split());x,t=10**9+7,[set()for _ in range(n)]
for i in range(n-1):;a,b=map(int,input().split());t[a-1].add(b);t[b-1].add(a)
c=k
def b(o):
  for i,j in enumerate(t[o-1]):c=(c*(k-2-i))%x;t[j-1].discard(o);b(j)
for i,j in enumerate(t[0]):c=(c*(k-1-i))%x;t[j-1].discard(1);b(j)
print(c)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(20000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0 and b:print(0);b=False
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
if b:print(ans)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(20000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(10000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)

Fixed submission:
import sys
sys.setrecursionlimit(100000)
n,k=map(int,input().split())
ans=k
t=[set()for i in range(n)]
dp=[k]+[0]*(n-1)
for i in range(n-1):
  a,b=map(int,input().split())
  t[a-1].add(b)
  t[b-1].add(a)
no=1
w=k
b=True
def a(noo):
  global ans
  w=k
  for i in t[noo-1]:
    t[i-1].discard(noo)
    if w==0:print(0);exit()
    dp[i-1]=w-2;ans=(ans*(w-2))%(10**9+7)
    w-=1
    a(i)
for i in t[no-1]:
  t[i-1].discard(no)
  w-=1
  dp[i-1]=w;ans=(ans*w)%(10**9+7)
  a(i)
print(ans)