Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left, bisect_right
from collections import deque
 
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):	
  	if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left, bisect_right
from collections import deque
 
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
    print(A)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left
from collections import deque
 
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.append(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
    A.extendleft(A_tmp)
                    
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        idx = bisect_left(A, pow2 - A[-1])
        for _ in range(idx):
            A_tmp.append(A.popleft())
        if len(A) < 2: break
        if A[0] + A[-1] == pow2:
            A.popleft()
            ans += 1
        A.pop()
        if len(A) < 2: break
    A = A_tmp + A
                    
print(ans)



Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from bisect import bisect_left, bisect_right

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

ans = 0
while len(A) > 1:
    pow2 = 1 << (len(bin(A[-1])) - 2)
    idx = bisect_left(A, pow2 - A[-1])
    if A[idx] + A[-1] == pow2 and idx != len(A) - 1:
        A.pop(idx)
        ans += 1
    A.pop()
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left, bisect_right
 
N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
 
ans = 0
while len(A) > 1:
    pow2 = 1 << (len(bin(A[-1])) - 2)
    idx = bisect_left(A, pow2 - A[-1])
    if A[idx] + A[-1] == pow2 and idx != len(A) - 1:
        A.pop(idx)
        ans += 1
    A.pop(-1)
print(ans)
from bisect import bisect_left, bisect_right

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

ans = 0
while len(A) > 1:
    pow2 = 1 << (len(bin(A[-1])) - 2)
    idx = bisect_left(A, pow2 - A[-1])
    if A[idx] + A[-1] == pow2 and idx != len(A) - 1:
        A.pop(idx)
        ans += 1
    A.pop()
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from bisect import bisect_left, bisect_right

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

ans = 0
while len(A) > 1:
    pow2 = 1 << (len(bin(A[-1])) - 2)
    idx = bisect_left(A, pow2 - A[-1])
    if A[idx] + A[-1] == pow2 and idx != len(A) - 1:
        A.pop(idx)
        ans += 1
    A.pop(-1)
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from bisect import bisect_left, bisect_right

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

ans = 0
while len(A) > 1:
    pow2 = 1 << (len(bin(A[-1])) - 2)
    idx = bisect_left(A, pow2 - A[-1])
    if A[idx] + A[-1] == pow2 and idx != len(A) - 1:
        A.pop(idx)
        ans += 1
    A.pop(-1)
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left, bisect_right

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

def bsearch_list(a, x):
    l = bisect_left(a, x)
    r = bisect_right(a, x)
    if l < r:
        return list(range(l, r))
    else:
        return []

pair_list = [[i, set()] for i in range(N)]
for t in range(1, 50):
    pow2 = 2 ** t
    if A[-1] * 2 < pow2:
        break
    for i in range(N):
        pair = set(bsearch_list(A, pow2 - A[i])) - {i}
        pair_list[i][1] = pair_list[i][1] | pair
        
pair_list_idx = [p[0] for p in sorted(pair_list, key=lambda x: len(x[1]))]
ans = 0
for i in pair_list_idx:
    if len(pair_list[i][1]) == 0: continue
    another = pair_list[i][1].pop()
    pair_list_idx.remove(another)
    ans += 1
print(ans)

Fixed submission:
from bisect import bisect_left, bisect_right
from collections import deque

N = int(input())
A = list(map(int, input().split(" ")))
A.sort()
A = deque(A)
ans = 0
t_max = len(bin(A[-1])) - 2
for t in range(t_max, 0, -1):
    if len(A) < 2: break
    while len(bin(A[-1])) - 2 > t:
        A.pop()
        if len(A) < 2: break
    if len(A) < 2: break
    pow2 = 1 << t
    A_tmp = deque()
    while t == len(bin(A[-1])) - 2:
        r = A.pop()
        idx = bisect_left(A, pow2 - r)
        for _ in range(idx):
            A_tmp.appendleft(A.popleft())
        if len(A) == 0: break
        if A[0] + r == pow2:
            A.popleft()
            ans += 1
        if len(A) < 2: break
    A.extendleft(A_tmp)
                    
print(ans)