Harryxun/GPT-100-sft-dataset huggingface dataset:
Problem p03911 (python)

Fixed submission:
from scipy.sparse import*
(n,m),*p=[map(int,t.split())for t in open(0)]
a,b,c=zip(*[(i,j+n-1,1)for i,q in enumerate(p)for j in list(q)[1:]])
print('YNEOS'[1in csgraph.connected_components(csr_matrix(((c,(a,b))),[n+m]*2))[1][:n]::2])

Buggy submission (verdict: Runtime Error):
from scipy.sparse import*
(n,m),*t=[map(int,t.split())for t in open(0)]
*b,a=zip(*[(i,j+n,1)for i,(_,*t)in enumerate(t)for j in t])
print('YNEOS'[1in csgraph.connected_components(csr_matrix((a,b),[n*m]*2))[1][:n]::2])

Buggy submission (verdict: Runtime Error):
from scipy.sparse import*
(n,m),*t=[map(int,t.split())for t in open(0)]
*b,a=zip(*[(i,j+n,1)for i,(_,*t)in enumerate(t)for j in t])
print('YNEOS'[1in csgraph.connected_components(csr_matrix((a,b),[n*9]*2))[1][:n]::2])

Buggy submission (verdict: Runtime Error):
from scipy.sparse import*
(n,m),*t=[map(int,t.split())for t in open(0)]
*b,a=zip(*[(i,j+n,1)for i,(_,*t)in enumerate(t)for j in t])
print('YNEOS'[1in csgraph.connected_components(csr_matrix((a,b),[m*9]*2))[1][:n]::2])

Buggy submission (verdict: Runtime Error):
from scipy.sparse import*
(n,m),*t=[map(int,t.split())for t in open(0)]
*b,a=zip(*[(i,j+n,1)for i,(_,*t)in enumerate(t)for j in t])
print('YNEOS'[1in csgraph.connected_components(csr_matrix((a,b),[m*3]*2))[1][:n]::2])

Buggy submission (verdict: Runtime Error):
from scipy.sparse import*
(n,m),*t=[map(int,t.split())for t in open(0)]
*b,a=zip(*[(i,j+n,1)for i,(_,*t)in enumerate(t)for j in t])
print('YNEOS'[1in csgraph.connected_components(csr_matrix((a,b),[n*3]*2))[1][:n]::2])

Buggy submission (verdict: Runtime Error):
from scipy.sparse import*;(n,m),*t=[map(int,t.split())for t in open(0)];*b,a=zip(*[(i,j+n-1,1)for i,(_,*t)in enumerate(t)for j in t]);print("YNEOS"[1in csgraph.connected_components(csr_matrix(((a,t)),[n+m]*2))[1][:n]::2])
Problem p02871 (python)

Fixed submission:
for i in range(10000): print(-1)

Buggy submission (verdict: Runtime Error):
import sys
from collections import deque
from heapq import heapify, heappop, heappush

def solve():
    inf = 100000000
    input = sys.stdin.readline
    
    V, E = map(int, input().split())
    edge = [[] for _ in range(V)]
    wf = dict()
    next_id = dict() #iからjに行くときにiの次に訪れる地点
    for i in range(V):
        wf[i] = dict()
        next_id[i] = dict()
        for j in range(V):
            next_id[i][j] = j
            wf[i][j] = (0 if i == j else inf)
    for _ in range(E):
        u, v, d = map(int, input().split())
        edge[u - 1].append((d, v - 1))
        edge[v - 1].append((d, u - 1))
        wf[u - 1][v - 1] = d
        wf[v - 1][u - 1] = d

    for k in range(V):
        for i in range(V):
            for j in range(V):
                if wf[i][j] > wf[i][k] + wf[k][j]:
                    wf[i][j] = wf[i][k] + wf[k][j]
                    next_id[i][j] = next_id[i][k] 

    T = int(input())
    order = set()
    stuck_order = set()

    command = [None] * T
    car_status = -2 #-2なら店、iならiへ向かって移動中
    heading = 0 #次に向かう地点
    dist_left = 0 #次に向かう地点までの残り距離
    final_dist = 0
    for t in range(T):
        N = int(input()) #注文の発生
        if N == 1:
            id, dst = map(int, input().split())
            if car_status == -2: order |= {dst - 1}
            else: stuck_order |= {dst - 1}
        
        if car_status == -2: #店にいるときの処理
            if order == {}: command[t] = -1
            else:
                for k in order:
                    final_dist = k
                    heading = next_id[0][k]
                    dist_left = edge[0][heading][0] - 1
                    car_status = heading
                    command[t] = heading
                    break
        
        else:
            if dist_left > 0:
                command[t] = heading
                dist_left -= 1
            else:
                if heading in order: order -= {heading} #荷物の積み下ろし

                if len(order) > 0: #まだ配達すべき荷物があるとき
                    for k in order:
                        current = heading
                        final_dist = k
                        heading = next_id[current][final_dist]
                        dist_left = edge[current][heading][0] - 1
                        car_status = heading
                        command[t] = heading
                        break
                
                else: #荷物が無いので店に戻る
                    final_dist = 0
                    current = heading
                    heading = next_id[current][final_dist]
                    dist_left = edge[current][heading][0] - 1
                    car_status = heading
                    command[t] = heading

    for t in command: print(t)

    return 0

if __name__ == "__main__":
    solve()
Problem p03975 (python)

Fixed submission:
N, A, B = map(int, raw_input().split())
t_list = list()
for i in range(N):
    t_list.append(int(raw_input()))

res = len(t_list) - len([t for t in t_list if t >= A and t < B])

print res

Buggy submission (verdict: Runtime Error):
import numpy as np

H, W = map(int, raw_input().split())
S_list = list()
for i in range(H):
    S_list.append(raw_input())


X_mat = np.zeros((H, W), dtype='int')
S_mat_extend = np.zeros((H+2, W+2), dtype='int')
# input
for h in range(H):
    for w in range(W):
        if S_list[h][w] == 'X':
            X_mat[h, w] += 1

# make graph
G = dict()
def add_node(s, Graph=G):
    Graph[s] = {'edges':dict()}
    
def add_edge(s, t, weight=1, Graph=G):
    Graph[s]['edges'][t] = weight

def max_flow(s, t, Graph=G):
    G_ = Graph
    flow = 0
    
    while True:
        # initialize
        for v in G_.keys():
            G_[v]['reach'] = -1
            G_[v]['path'] = ''
        G_[s]['reach'] = 1
        # bfs
        ques = [s]
        while len(ques) > 0:
            v = ques.pop()
            for d in G_[v]['edges'].keys():
                if G_[v]['edges'][d] > 0 and G_[d]['reach'] == -1:
                    # update
                    G_[d]['reach'] = 1
                    G_[d]['path'] = v
                    ques.append(d)
                    if d == t:
                        flow += 1
                        break

        if G_[t]['path'] != '':
            y = t
            while True:
                x = G_[y]['path']
                G_[x]['edges'][y] -= 1
                if x not in Graph[y]['edges'].keys():
                    add_edge(y, x, weight=0, Graph=G_)
                G_[y]['edges'][x] += 1
                if x == s:
                    break
                else:
                    y = x
        else:
            break
    
    return flow


# src:sheeps
# dst:outer
add_node('src')
add_node('dst')

# grid
for i in range(H):
    for j in range(W):
        add_node(str([i, j]) + '-src')
        add_node(str([i, j]) + '-dst')
        add_edge(str([i, j]) + '-dst', str([i, j]) + '-src')
        if X_mat[i, j] == 1:
            add_edge('src', str([i, j]) + '-dst', 100000)
            add_edge(str([i, j]) + '-dst', str([i, j]) + '-src', 100000)
        if i > 0:
            add_edge(str([i, j]) + '-src', str([i-1, j]) + '-dst')
        if i < H-1:
            add_edge(str([i, j]) + '-src', str([i+1, j]) + '-dst')
        if j > 0:
            add_edge(str([i, j]) + '-src', str([i, j-1]) + '-dst')
        if j < W-1:
            add_edge(str([i, j]) + '-src', str([i, j+1]) + '-dst')
        if i == 0 or j == 0 or i == H-1 or j == W-1:
            add_edge(str([i, j]) + '-src', 'dst', 100000)

res = 0
# find -1
if X_mat[0,:].sum() + X_mat[H-1,:].sum() + X_mat[:,0].sum() + X_mat[:,W-1].sum() > 0:
    res = -1
else:
    res = max_flow('src', 'dst')


print res
Problem p03125 (python)

Fixed submission:
A, B = map(int, input().split())
print(A + B if B % A == 0 else B - A)

Buggy submission (verdict: Runtime Error):
A, B = map(int, input())
print(A + B if B % A == 0 else B - A)
Problem p03126 (python)

Fixed submission:
N, M = map(int, input().split())
 
all_set = set.intersection(*map(set, (
  list(map(int, input().split()))[1:]
  for i in range(N)
)))
 
print(len(all_set))

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

all_set = set.intersection(*map(set, (
  list(map(int, input().split()))[1:]
  for i in range(N)
))

print(len(all_set))
Problem p03128 (python)

Fixed submission:
import sys
sys.setrecursionlimit(100000)

N, M = map(int, input().split())
numbers = list(map(int, input().split()))
costs = [2,5,5,4,5,6,3,7,6] # <- 1,2,3,4,5,6,7,8,9
costmap = {}
for num in numbers:
  cost = costs[num-1]
  if cost in costmap and num < costmap[cost]:
    continue
  costmap[cost] = num

from functools import lru_cache
@lru_cache(None)
def recursive(remain=N):
  maxval = costmap[remain] if remain in costmap else 0
  for cost, num in costmap.items():
    if remain > cost:
      val = recursive(remain-cost)
      if val == 0:
        continue
      val = val * 10 + num
      if val > maxval:
        maxval = val
  return maxval
 
print(recursive(N))

Buggy submission (verdict: Runtime Error):
N, M = map(int, input().split())
numbers = set(map(int, input().split()))
costs = [2,5,5,4,5,6,3,7,6] # <- 1,2,3,4,5,6,7,8,9
costmap = {}
for num in numbers:
  cost = costs[num-1]
  if cost in costmap and num < costmap[cost]:
    continue
  costmap[cost] = num

from functools import lru_cache
@lru_cache(None)
def recursive(remain=N):
  maxval = costmap[remain] if remain in costmap else 0
  for cost, num in costmap.items():
    if remain > cost:
      val = recursive(remain-cost)
      if val is None:
        continue
      val = val * 10 + num
      if val > maxval:
        maxval = val
  if maxval == 0:
    return None
  return maxval

print(recursive(N))

Buggy submission (verdict: Runtime Error):
N, M = map(int, input().split())
numbers = set(map(int, input().split()))
costs = [2,5,5,4,5,6,3,7,6] # <- 1,2,3,4,5,6,7,8,9
costmap = {}
for num in numbers:
  cost = costs[num-1]
  if cost in costmap and num < costmap[cost]:
    continue
  costmap[cost] = num

def recursive(remain=N):
  maxval = costmap[remain] if remain in costmap else 0
  for cost, num in costmap.items():
    if remain > cost:
      val = recursive(remain-cost)
      if val is None:
        continue
      val = val * 10 + num
      if val > maxval:
        maxval = val
  if maxval == 0:
    return None
  return maxval

print(recursive(N))
Problem p03150 (python)

Fixed submission:
import sys
S = input().strip()
keyence = "keyence"
n = len(keyence)

if keyence in S:
    k = S.find(keyence)
    if k == 0:
        print("YES")
        sys.exit()
    elif k + n == len(S):
        print("YES")
        sys.exit()

for i in range(n):
    if S[:i] == keyence[:i] and S[-(n-i):] == keyence[-(n-i):]:
        print("YES")
        sys.exit()

print("NO")

Buggy submission (verdict: Runtime Error):
import sys
S = input().strip()
keyence = "keyence"

for i in range(len(keyence)):
    if keyence[:i] in S:
        s = S.find(keyence[:i]) + i
        S2 = S[s:]
        if keyence[i:] in S2:
            print("YES")
            sys.exit()

print("NO")
~
Problem p02882 (python)

Fixed submission:
import math

a,b,x = map(int,input().split())

if a**2*b == x:
    print(0)
elif a**2 * b < 2*x:
    print(90-math.degrees(math.atan((1/2*a**3)/(a**2*b-x))))
else:
    print(math.degrees(math.atan((1/2*a*b**2)/(x))))

Buggy submission (verdict: Runtime Error):
import math

a,b,x = map(int,input().split())

if a**2 * b < 2*x:
    print(90-math.degrees(math.atan((1/2*a**3)/(a**2*b-x))))
else:
    print(math.degrees(math.atan((1/2*a*b**2)/(x))))
Problem p02885 (python)

Fixed submission:
A,B = map(int,input().split())
ans = A - B*2
if ans < 0 :
    print(0)
else:
    print(ans)

Buggy submission (verdict: Runtime Error):
N = int(input())
l = map(int,input().split())
l = sorted(l)
l_dict = dict()
max_l  = max(l)
min_l = min(l)
t_list = [one for one in l if one+min_l < max_l]
for i,one in enumerate(t_list):
    l_dict[one] = i
    
    
big_dict = dict()
for one in t_list:
    big_dict[one] = bisect.bisect_left(l,2*one)

counter = 0

for a,b in combinations(t_list,2):
    tmp = a + b
    counter += bisect.bisect_left(l[l_dict[b]+1:big_dict[b]],tmp)
    
print(counter)
Problem p02963 (python)

Fixed submission:
#!/usr/bin/env python
# coding: utf-8

# In[76]:


s = int(input())
s_str = str(s)
order = len(s_str)

tmp_list = [s_str[i] for i in range(len(s_str))]
if set(tmp_list) == set(["0","1"]):
    if len(s_str) <= 10:
        a = s
        b = 1
        c = 1
        d = 0
    else:
        a = 10**9
        b = 10**(len(s_str)-10)
        c = 1
        d = 0
elif len(s_str) >= 10:
    a = int(s_str[:9]) +1
    b = 10**(len(s_str) - 9)
    c = 10**(len(s_str[9:])) - int(s_str[9:])
    d = 1
else:
    a = int(s_str)
    b = 1
    c = 1
    d = 0

print('0 0 ' + str(a) + ' ' + str(d) + ' ' + str(c) + ' ' + str(b))


# In[ ]:

Buggy submission (verdict: Runtime Error):
#!/usr/bin/env python
# coding: utf-8

# In[ ]:


s = int(input())
s = random.randint(1,10**18)

s_str = str(s)
order = len(s_str)

if len(s_str) >= 10:
    a = int(s_str[:9]) +1
    b = 10**(len(s_str) - 9)
    c = 10**(len(s_str[9:])) - int(s_str[9:])
    d = 1
else:
    a = int(s_str)
    b = 1
    c = 1
    d = 0

print('0 0 ' + str(a) + ' ' + str(d) + ' ' + str(c) + ' ' + str(b))
Problem p03628 (python)

Fixed submission:
N = int(input())
A = input()
B = input()

def f(horizontal_flag):
    if horizontal_flag[0]:
        if horizontal_flag[1]:
            return 3
        else:
            return 1
    else:
        return 2

if N == 1:
    print(3)    
else:
    if A[0] == A[1]:
        counter = 6
        initial_num = 2
        horizontal_flag = [1,0]
    else:
        counter = 3
        initial_num = 1
        horizontal_flag = [0,0]

    for i in range(initial_num,N):
        if i == N-1:
            if horizontal_flag[1] == 2:
                horizontal_flag[1] = 1
                counter *= f(horizontal_flag)
            else:
                horizontal_flag[1] = 0
                counter *= f(horizontal_flag)
        elif A[i] == A[i+1]:
            horizontal_flag[1] = 2
        else:
            if horizontal_flag[1] == 2:
                horizontal_flag[1] = 1
                counter *= f(horizontal_flag)
            else:
                horizontal_flag[1] = 0
                counter *= f(horizontal_flag)
            horizontal_flag[0] = horizontal_flag[1]
    print(counter % 1000000007)

Buggy submission (verdict: Runtime Error):
def f(horizontal_flag):
    if horizontal_flag[0]:
        if horizontal_flag[1]:
            return 3
        else:
            return 1
    else:
        return 2

if N == 1:
    print(3)    
else:
    if A[0] == A[1]:
        counter = 6
        initial_num = 2
        horizontal_flag = [0,1]
    else:
        counter = 3
        initial_num = 1
        horizontal_flag = [0,1]


    for i in range(initial_num,N):
        if i == N-1:
            if horizontal_flag[1] == 2:
                horizontal_flag[1] = 1
                counter *= f(horizontal_flag)
            else:
                horizontal_flag[1] = 0
                counter *= f(horizontal_flag)
        elif A[i] == A[i+1]:
            horizontal_flag[1] = 2
        else:
            if horizontal_flag[1] == 2:
                horizontal_flag[1] = 1
                counter *= f(horizontal_flag)
            else:
                horizontal_flag[1] = 0
                counter *= f(horizontal_flag)
            horizontal_flag[0] = horizontal_flag[1]
    print(counter % 1000000007)
Problem p02903 (python)

Fixed submission:
h, w, a, b = map(int, input().split())
for i in range(h):
  if i < b:
    print("0"*a + "1"*(w-a))
  else:
    print("1"*a + "0"*(w-a))

Buggy submission (verdict: Runtime Error):
h, w, a, b = map(int, input().split())
mx = [[0 for i in range(w)] for _ in range(h)]
for k in range(a):
  mx[0][k] = 1

for i in range(b):
  mx[i][0] = 1

if w == 1 and a != 0:
  print("No")
elif w == 1 and a == 0:
  for j in range(h):
    s = [str(x) for x in mx[j]]
    print("".join(s))
elif h == 1 and b != 0:
  print("No")
elif h == 1 and b == 0:
  for j in range(h):
    s = [str(x) for x in mx[j]]
    print("".join(s))
else:
  pr = 1
  pc = 1

  while pr < w:
    for k in range(pc, pc + a - sum(mx[pr][:pc])):
      if k >= w:
        print("No")
        exit()
      else:
        mx[pr][k] = 1

    csum = 0
    for i in range(pr):
      csum += mx[i][pc]
    for i in range(pr, pr + b - csum):
      mx[i][pc] = 1
    pr += 1
    if pc < w - 1:
      pc += 1

  flg = 0
  for j in range(w):
    bsum = sum(mx[:][j])
    if min(bsum, h - bsum) != b:
      flg = 1
      break

  if flg == 1:
    print("No")
  else:
    for j in range(h):
      s = [str(x) for x in mx[j]]
      print("".join(s))

Buggy submission (verdict: Runtime Error):
h, w, a, b = map(int, input().split())
mx = [[0 for i in range(w)] for _ in range(h)]
for k in range(a):
  mx[0][k] = 1

for i in range(b):
  mx[i][0] = 1

if w == 1 and a != 0:
  print("No")
elif w == 1 and a == 0:
  for j in range(h):
    s = [str(x) for x in mx[j]]
    print("".join(s))
elif h == 1 and b != 0:
  print("No")
elif h == 1 and b == 0:
  for j in range(h):
    s = [str(x) for x in mx[j]]
    print("".join(s))
else:
  pr = 1
  pc = 1

  while pr < w:
    print(pr, pc, mx)
    for k in range(pc, pc + a - sum(mx[pr][:pc])):
      mx[pr][k] = 1

    csum = 0
    for i in range(pr):
      csum += mx[i][pc]
    for i in range(pr, pr + b - csum):
      mx[i][pc] = 1
    pr += 1
    pc += 1

  flg = 0
  for j in range(w):
    bsum = sum(mx[:][j])
    if min(bsum, h - bsum) != b:
      flg = 1
      break

  if flg == 1:
    print("No")
  else:
    for j in range(h):
      s = [str(x) for x in mx[j]]
      print("".join(s))

Buggy submission (verdict: Runtime Error):
import itertools

def main():
    h, w, a, b = map(int, input().split())
    mx_0 = [[1 if i < a else 0 for i in range(w)]]
    s01 = [1 if i < a else 0 for i in range(w)]
    ss = list(set(itertools.permutations(s01, w)))
    if a != w - a:
        s10 = [0 if i < a else 1 for i in range(w)]
        ss10 = list(set(itertools.permutations(s10, w)))
        ss.extend(ss10)

    mx01 = list(set(itertools.permutations(ss, h - 1)))
    for m in mx01:
        mx = mx_0.copy()
        mx.extend(m)
        flg = 1
        for i in range(w):
            b01 = [x[i] for x in mx]
            bsum = sum(b01)
            if min(bsum, h - bsum) != b:
                flg = 0
        if flg == 1:
            for j in range(h):
                s = [str(x) for x in mx[j]]
                print("".join(s))
            return

    print("No")
    return

main()
Problem p02913 (python)

Fixed submission:
N = int(input())
s = input()

dp = [[0 for _ in range(N+1)] for _ in range(N+1)]

for i in range(N-1, -1, -1):
  for j in range(N-1, -1, -1):
    if s[i] != s[j]:
      dp[i][j] = 0
    else:
      dp[i][j] = dp[i+1][j+1] + 1
    
ans = 0
for i in range(N):
  for j in range(N):
    if i >= j:
      continue
    now = min(dp[i][j], j - i)
    ans = max(ans, now)
print(ans)

Buggy submission (verdict: Runtime Error):
N = int(input())
s = input()

dp = [[0 for _ in range(N+1)] for _ in range(N+1)]

for i in range(N-1, 0, -1):
  for j in range(N-1, 0, -1):
    if s[i] != s[j]:
      dp[i][j] = 0
    else:
      dp[i][j] = dp[i+1][j+1] + 1
    
ans = 0
for i in range(N):
  for j in range(N):
    if i >= j:
      continue
    now = min(dp[i][j], j - i)
    ans = max(ans, now)
print(ans)
Problem p02918 (python)

Fixed submission:
N, K = map(int, input().split())
S = input()
max_happy = N-1
init_happy = 0
for i in range(1, N-1):
  if S[i]=="L" and S[i-1]=="L":
    init_happy += 1
  elif S[i]=="R" and S[i+1]=="R":
    init_happy += 1

if N>1:
  if S[0]=="R" and S[1]=="R":
    init_happy += 1

  if S[-1]=="L" and S[-2]=="L":
    init_happy += 1

ans = min(max_happy, init_happy+K*2)

print(ans)

Buggy submission (verdict: Runtime Error):
N, K = map(int, input().split())
S = input()
max_happy = N-1
init_happy = 0
for i in range(1, N-1):
  if S[i]=="L" and S[i-1]=="L":
    init_happy += 1
  elif S[i]=="R" and S[i+1]=="R":
    init_happy += 1

if S[0]=="R" and S[1]=="R":
  init_happy += 1

if S[-1]=="L" and S[-2]=="L":
  init_happy += 1

ans = min(max_happy, init_happy+K*2)

print(ans)
Problem p02952 (python)

Fixed submission:
N = int(input())
n = N
cnt = 0
while n>0:
  n = n//10
  cnt += 1

if cnt==1:
  print(N)
else:
  tmp = "90"*(cnt//2)
  tmp = int(tmp[:-1])

  if cnt%2!=0:
    tmp += N-int("9"*(cnt-1))

  print(tmp)

Buggy submission (verdict: Runtime Error):
N = int(input())
n = N
cnt = 0
while n>0:
  n = n//10
  cnt += 1

tmp = "90"*(cnt//2)
tmp = int(tmp[:-1])

if cnt%2!=0:
  tmp += N-int("9"*(cnt-1))

print(tmp)
Problem p02963 (python)

Fixed submission:
# 解説YouTubeをもとに
# https://atcoder.jp/contests/agc036/submissions/6943945 参考
S = int(input())
x1, y1, x2, y2 = 0, 0, 10**9, 1
if S==10**18:
  print(x1, y1, x2, y2, 0, x2)
else:
  y3 = S//x2 + 1
  x3 = x2*y3 - S
  print(x1, y1, x2, y2, x3, y3)

Buggy submission (verdict: Runtime Error):
# 解説YouTubeをもとに
S = int(input())
x1, y1, x2, x3 = 0, 0, 10**9, 1
if S==10**18:
  print(x1, y1, x2, y2, 0, x2)
else:
  y3 = S//x2 + 1
  y2 = x2*y3 - S
  print(x1, y1, x2, y2, x3, y3)
Problem p03569 (python)

Fixed submission:
s = input()

cnt = 0
ans = 0

if len(s) == 1:
    cnt = 0
else:
    l = 0
    k = 0
    while True:
        if s[l] == s[-k-1]:
            l += 1
            k += 1
            if l + k >= len(s)-1:
                break
        elif s[l] == 'x':
            l += 1
            cnt += 1
            if l + k >= len(s)-1:
                break
        elif s[-k-1] == 'x':
            k += 1
            cnt += 1
            if l + k >= len(s)-1:
                break
        else:
            ans = -1
            break

if ans == -1:
    print(ans)
else:
    print(cnt)

Buggy submission (verdict: Runtime Error):
s = input()

x = -1

if len(s) == 1:
    x = 0
else:
    s2 = s.replace('x', '')

    if len(s2) % 2 == 0:
        flg = True
    else:
        flg = False

    nf = len(s2) // 2

    if flg:
        s2_pre = s2[:nf+1]
        s2_post = s2[nf+1:]
    else:
        s2_pre = s2[:nf]
        s2_post = s2[nf+1:]

    if s2_pre == s2_post[::-1]:
        cnt_s = 0
        cnt_s2 = 0
        while True: # 元の文字列の中心を求める
            if s[cnt_s] == 'x':
                cnt_s += 1
            if s[cnt_s] == s2[cnt_s2]:
                cnt_s += 1
                cnt_s2 += 1
            if cnt_s2 >= nf:
                break

        if len(s) % 2 == 0:
            s_pre = s[:cnt_s+1]
            s_post = s[cnt_s+1:]
        else:
            s_pre = s[:cnt_s]
            s_post = s[cnt_s+1:]

        s_postR = s_post[::-1]

        s_pre = list(s_pre)
        s_postR =  list(s_postR)

        cnt = 0
        cnt_pre = 0
        cnt_post = 0
        while True:
            try:
                if s_pre[cnt_pre] == s_postR[cnt_post]:
                    cnt_pre += 1
                    cnt_post += 1
            except IndexError:
                pass
            
            if len(s_pre) > cnt_pre:
                if s_pre[cnt_pre] == 'x':
                    s_postR.insert(cnt_post, 'x')
                    cnt_pre += 1
                    cnt_post += 1
                    cnt += 1
            elif len(s_postR) > cnt_post:
                if str(s_pre) == str(s_postR):
                    break
                else:
                    s_pre.insert(cnt_pre, s_postR[cnt_post])
                    cnt_pre += 1
                    cnt_post += 1
                    cnt += 1
                    
            if len(s_postR) > cnt_post:
                if s_postR[cnt_post] == 'x':
                    s_pre.insert(cnt_pre, 'x')
                    cnt_pre += 1
                    cnt_post += 1
                    cnt += 1
            elif len(s_pre) > cnt_pre:
                if str(s_pre) == str(s_postR):
                    break
                else:
                    s_postR.insert(cnt_post, s_pre[cnt_pre])
                    cnt_pre += 1
                    cnt_post += 1
                    cnt += 1

            if str(s_pre) == str(s_postR):
                break

        x = cnt
    
print(x)