Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(200000)
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)
 
n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [None] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)
 
def erase(v):
  if s[v] == "A":
    l = 0
  else:
    l = 1
  for q in links[v][0]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = None
      erase(q)
  for q in links[v][1]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = None
      erase(q)  
for i in range(n):
  if not able[i]:
    continue
  for k in range(2):
    for j in links[i][k].copy():
      if not able[j]:
        links[i][k].remove(j)
  if (links[i][0] == set() or links[i][1] == set()):
    flag =1
    able[i] = None
    erase(i)
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10**7)
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)
 
n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [None] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)

used = [None]*n
def erase(v):
  if s[v] == "A":
    l = 0
  else:
    l = 1
  for q in links[v][0]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      used[q] = True
      erase(q)
  for q in links[v][1]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      used[q] = True
      erase(q)

for i in range(n):
  if not able[i]:
    if not used[i]:
      erase(i)
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10**7)
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)
 
n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)

used = [False]*n
def erase(v):
  if s[v] == "A":
    l = 0
  else:
    l = 1
  for q in links[v][0]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      used[q] = True
      erase(q)
  for q in links[v][1]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      used[q] = True
      erase(q)

for i in range(n):
  if not able[i]:
    if not used[i]:
      erase(i)
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(10**7)
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)
 
n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)
 
def erase(v):
  if s[v] == "A":
    l = 0
  else:
    l = 1
  for q in links[v][0]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      erase(q)
  for q in links[v][1]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      erase(q)

for i in range(n):
  if not able[i]:
    erase(i)
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10**7)
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)

n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)

def erase(v):
  if s[v] == "A":
    l = 0
  else:
    l = 1
  for q in links[v][0]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      erase(q)
  for q in links[v][1]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      erase(q)

for i in range(n):
  if not able[i]:
    continue
  for k in range(2):
    for j in links[i][k].copy():
      if not able[j]:
        links[i][k].remove(j)
  if (links[i][0] == set() or links[i][1] == set()):
    flag =1
    able[i] = False
    erase(i)
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10**7)
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)

n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)

def erase(v):
  if s[v] == "A":
    l = 0
  else:
    l = 1
  for q in links[v][0]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      erase(q)
  for q in links[v][1]:
    if not able[q]:
      continue
    links[q][l].remove(v)
    if links[q][l] == set():
      able[q] = False
      erase(q)  
for i in range(n):
  if not able[i]:
    continue
  for k in range(2):
    for j in links[i][k].copy():
      if not able[j]:
        links[i][k].remove(j)
  if (links[i][0] == set() or links[i][1] == set()):
    flag =1
    able[i] = False
    erase(i)
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
import sys
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)

n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)
flag = 1
tmp = set()
for i in range(n):
  if able[i]:
    tmp.add(i)
while flag ==1:
  flag = 0
  for i in tmp.copy():
    if not able[i]:
      continue
    for k in range(2):
      for j in links[i][k].copy():
        if not able[j]:
          links[i][k].remove(j)
    if (links[i][0] == set() or links[i][1] == set()):
      flag =1
      tmp.remove(i)
      able[i] = False
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Runtime Error):
import sys
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)

n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)
flag = 1
tmp = set()
for i in range(n):
  if able[i]:
    tmp.add(i)
while flag ==1:
  flag = 0
  for i in tmp:
    if not able[i]:
      continue
    for k in range(2):
      for j in links[i][k].copy():
        if not able[j]:
          links[i][k].remove(j)
    if (links[i][0] == set() or links[i][1] == set()):
      flag =1
      tmp.remove(i)
      able[i] = False
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
import sys
def add_link(a, b):
    la = links[a]
    i, j = [(0, 1), (1, 0)][s[b] == 'B']
    if not la[i] and la[j]:
        able[a] = True
    la[i].add(b)

n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False] * n
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    add_link(a, b)
    add_link(b, a)
flag = 1
while flag ==1:
  flag = 0
  for i in range(n):
    if not able[i]:
      continue
    for k in range(2):
      for j in links[i][k].copy():
        if not able[j]:
          links[i][k].remove(j)
    if (links[i][0] == set() or links[i][1] == set()):
      flag =1
      able[i] = False
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")

Buggy python submission (verdict: Time Limit Exceeded):
n, m = map(int, input().split())
s = input()
links = [[set(), set()] for _ in range(n)]
able = [False]
p = []
for i in range(m):
    p.append(list(map(int, input().split())))
l = [set() for i in range(n+1)]
for pi in p: 
    l[pi[0]].add(pi[1])
    l[pi[1]].add(pi[0])

while True:
  ans = able.count(True)
  able = [False]*(n+1)
  for i in range(1,n+1):
    ab = 0
    for j in l[i]:
      if s[j-1] == "A":
        ab |= 1
      else:
        ab |= 2
      if ab == 3:
        able[i] = True
        break
  for i in range(1,n+1):
    for j in l[i].copy():
      if not able[j]:
        l[i].remove(j)
  tmp = able.count(True)
  if ans == tmp:
    break
if any(able):
  print("Yes")
else:
  print("No")

Fixed submission:
import sys
sys.setrecursionlimit(1000000)
n, m = map(int, input().split())
s = input()
links = [[] for _ in range(2*n)]
visit = [0] * n *2
for line in sys.stdin.readlines():
    a, b = map(int, line.split())
    a -= 1
    b -= 1
    if s[a] == s[b]:
      links[a].append(b+n)
      links[b].append(a+n)
    else:
      links[a+n].append(b)
      links[b+n].append(a)
def dfs(v):
  visit[v] = 1
  for i in links[v]:
    if visit[i] == 1:
      print("Yes")
      exit()
    elif visit[i] == 0:
      dfs(i)
  visit[v] = -1
  
for i in range(n):
  if visit[i] == 0:
    dfs(i)
print("No")