Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
used_ball = [False] * N

for i in reversed(range(0, len(A))):
    if used_ball[i]:
        continue
    for j in reversed(range(0, i)):
        if used_ball[j]:
            continue
        if not ((A[i] + A[j]) & (A[i] + A[j] - 1)):
            n_pears += 1
            used_ball[j] = True
            break

print(n_pears)

Fixed submission:
import math
from collections import Counter


N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
counter = Counter(A)

for i in reversed(range(0, len(A))):
    if counter[A[i]] <= 0:
        continue
    counter[A[i]] -= 1
    Aj = 2 ** int(math.log2(A[i]) + 1) - A[i]
    if counter[Aj] > 0:
        n_pears += 1
        counter[Aj] -= 1

print(n_pears)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
used_balls = []

for i in reversed(range(0, len(A))):
    if i % 1000 == 0:
        used_balls.sort()
        for n in used_balls:
            if i <= n:
                del used_balls[n:]
            break
        if i == n:
            continue
    if i in used_balls:
        continue
    for j in reversed(range(0, i)):
        if j in used_balls:
            continue
        if not ((A[i] + A[j]) & (A[i] + A[j] - 1)):
            n_pears += 1
            used_balls.append(j)
            break

print(n_pears)

Fixed submission:
import math
from collections import Counter


N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
counter = Counter(A)

for i in reversed(range(0, len(A))):
    if counter[A[i]] <= 0:
        continue
    counter[A[i]] -= 1
    Aj = 2 ** int(math.log2(A[i]) + 1) - A[i]
    if counter[Aj] > 0:
        n_pears += 1
        counter[Aj] -= 1

print(n_pears)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
used_balls = []

for i in reversed(range(0, len(A))):
    if i in used_balls:
        continue
    for j in reversed(range(0, i)):
        if j in used_balls:
            continue
        if not ((A[i] + A[j]) & (A[i] + A[j] - 1)):
            n_pears += 1
            used_balls.append(j)
            break

print(n_pears)

Fixed submission:
import math
from collections import Counter


N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
counter = Counter(A)

for i in reversed(range(0, len(A))):
    if counter[A[i]] <= 0:
        continue
    counter[A[i]] -= 1
    Aj = 2 ** int(math.log2(A[i]) + 1) - A[i]
    if counter[Aj] > 0:
        n_pears += 1
        counter[Aj] -= 1

print(n_pears)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
used_balls = []

for i in reversed(range(0, len(A))):
    if i in used_balls:
        continue
    for j in reversed(range(0, i)):
        if j in used_balls:
            continue
        if not (A[i] + A[j]) & (A[i] + A[j] - 1):
            n_pears += 1
            used_balls.append(i)
            used_balls.append(j)
            break

print(n_pears)

Fixed submission:
import math
from collections import Counter


N = int(input())
A = list(map(int, input().split()))
A.sort()

n_pears = 0
counter = Counter(A)

for i in reversed(range(0, len(A))):
    if counter[A[i]] <= 0:
        continue
    counter[A[i]] -= 1
    Aj = 2 ** int(math.log2(A[i]) + 1) - A[i]
    if counter[Aj] > 0:
        n_pears += 1
        counter[Aj] -= 1

print(n_pears)