Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    check = deque()
    def my_index(l, x, default=False):
        return l.index(x) if x in l else default

    for _ in range(N):
        A = int(input())
        if A not in check:
            check.append(A)
        else:
            check.remove(A)
    print(len(check))

if __name__ == "__main__":
    main()

Fixed submission:
from collections import Counter
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    A = [input() for _ in range(N)]
    common = Counter(A).most_common()
    ans = 0
    for i in common:
        if i[1] % 2 == 1:
            ans += 1
    print(ans)
    
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    check = deque()
    def my_index(l, x, default=False):
        return l.index(x) if x in l else default

    for _ in range(N):
        A = int(input())
        if A not in check:
            check.append(A)
        else:
            check.remove(A)
    print(len(check))

if __name__ == "__main__":
    main()

Fixed submission:
from collections import Counter
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    A = [input() for _ in range(N)]
    common = Counter(A).most_common()
    ans = 0
    for i in common:
        if i[1] % 2 == 1:
            ans += 1
    print(ans)
    
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    check = []
    def my_index(l, x, default=False):
        return l.index(x) if x in l else default

    for _ in range(N):
        A = int(input())
        if A not in check:
            check.append(A)
        else:
            del check[my_index(check,A)]
    print(len(check))

if __name__ == "__main__":
    main()

Fixed submission:
from collections import Counter
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    A = [input() for _ in range(N)]
    common = Counter(A).most_common()
    ans = 0
    for i in common:
        if i[1] % 2 == 1:
            ans += 1
    print(ans)
    
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    check = []
    def my_index(l, x, default=False):
        return l.index(x) if x in l else default

    for _ in range(N):
        A = int(input())
        if A not in check:
            check.append(A)
        else:
            del check[my_index(check,A)]
    print(len(check))

if __name__ == "__main__":
    main()

Fixed submission:
from collections import Counter
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    A = [input() for _ in range(N)]
    common = Counter(A).most_common()
    ans = 0
    for i in common:
        if i[1] % 2 == 1:
            ans += 1
    print(ans)
    
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
check = []
def my_index(l, x, default=False):
    return l.index(x) if x in l else default

for _ in range(N):
    A = int(input())
    if A not in check:
        check.append(A)
    else:
        del check[my_index(check,A)]
print(len(check))

Fixed submission:
from collections import Counter
import sys

def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    A = [input() for _ in range(N)]
    common = Counter(A).most_common()
    ans = 0
    for i in common:
        if i[1] % 2 == 1:
            ans += 1
    print(ans)
    
if __name__ == "__main__":
    main()