Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    c = Counter(A)
    B = sorted(c.keys(), reverse=True)

    for b in B:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            if a in c.keys():
                cur = min(c[a], c[b])
            else:
                cur = 0
        ans += cur
        # c[b] -= cur
        c[a] -= cur

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = dict(Counter(A))

    for b in A:
        if c[b] == 0:
            continue
        a = (1 << b.bit_length()) - b
        if a == b:
            ans += c[b]//2
            c[b] %= 2
        else:
            if a in c.keys() and c[a] > 0:
                cur = min(c[a], c[b])
                ans += cur
                c[b] -= cur
                c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (1 << b.bit_length()) - b
        if a == b:
            ans += c[b]//2
            c[b] %= 2
        else:
            if a in c.keys() and c[a] > 0:
                cur = min(c[a], c[b])
                ans += cur
                c[b] -= cur
                c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        a = (1 << b.bit_length()) - b
        if a == b:
            ans += c[b]//2
            c[b] %= 2
        else:
            if a in c.keys():
                cur = min(c[a], c[b])
                ans += cur
                c[b] -= cur
                c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        a = (2**b.bit_length()) - b
        if a == b:
            ans += c[b]//2
            c[b] %= 2
        else:
            if a in c.keys():
                cur = min(c[a], c[b])
                ans += cur
                c[b] -= cur
                c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
def main():
    from collections import Counter
    from bisect import bisect
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)
    bi = [2**i for i in range(1, 15)]

    for b in A:
        a = (bi[bisect(bi, b)]) - b
        if a == b:
            ans += c[b]//2
            c[b] %= 2
        else:
            if a in c.keys():
                cur = min(c[a], c[b])
                ans += cur
                c[b] -= cur
                c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from collections import Counter
    from bisect import bisect
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)
    bi = [2**i for i in range(1, 31)]

    for b in A:
        a = (bi[bisect(bi, b)]) - b
        if a == b:
            ans += c[b]//2
            c[b] %= 2
        else:
            if a in c.keys():
                cur = min(c[a], c[b])
                ans += cur
                c[b] -= cur
                c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
def main():
    from collections import Counter
    import sys
    input = sys.stdin.buffer.readline

    _ = int(input())
    A = [int(i) for i in input().split()]

    ans = 0
    A.sort(reverse=True)
    c = Counter(A)

    for b in A:
        if c[b] == 0:
            continue
        a = (2 ** b.bit_length()) - b
        if a == b:
            cur = c[b]//2
        else:
            cur = min(c[a], c[b])
        ans += cur
        c[b] -= cur
        c[a] -= cur
        # print(a, b, c, ans)

    print(ans)


if __name__ == '__main__':
    main()