Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    for i in sorted(Ad.copy().keys()):
        if i >= k:
            break
        if 2*i == k:
            ans += Ad[i]//2
            del Ad[i]
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            del Ad[i]
            ans += m
        else:
            H[i] = j
print(ans)


Fixed submission:
import bisect
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
A = list(set(A))
A.sort()
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    ml = bisect.bisect_left(A, k) 
    for i in A[:ml]:
        if 2*i == k:
            ans += Ad[i]//2
            del Ad[i]
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            del Ad[i]
            ans += m
        else:
            H[i] = j
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    for i, j in Ad.copy().items():
        if 2*i == k:
            ans += Ad[i]//2
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            Ad[i] -= m
            ans += m
        else:
            H[i] = j
print(ans)


Fixed submission:
import bisect
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
A = list(set(A))
A.sort()
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    ml = bisect.bisect_left(A, k) 
    for i in A[:ml]:
        if 2*i == k:
            ans += Ad[i]//2
            del Ad[i]
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            del Ad[i]
            ans += m
        else:
            H[i] = j
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    for i, j in Ad.copy().items():
        if 2*i == k:
            m = Ad[i]//2
            Ad[i] -= 2*m
            ans += m
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            Ad[i] -= m
            ans += m
        else:
            H[i] = j
print(ans)

Fixed submission:
import bisect
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
A = list(set(A))
A.sort()
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    ml = bisect.bisect_left(A, k) 
    for i in A[:ml]:
        if 2*i == k:
            ans += Ad[i]//2
            del Ad[i]
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            del Ad[i]
            ans += m
        else:
            H[i] = j
print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
def list_dif(l1, l2):
    result = l1.copy()
    for v in l2:
        if v in result:
            result.remove(v)
    return result
H = defaultdict(lambda: [])
N = int(input())
A = sorted(inpl())
ans = 0
for j in range(29,0,-1):
    k = 2**j
    t = []
    H = defaultdict(lambda: [])
    for i in A:
        if k <= i:
            break
        if H[k-i]:
            t.append(H[k-i].pop())
            t.append(i)
            ans += 1
        else:
            H[i].append(i)
    A = list_dif(A, t)
print(ans)

Fixed submission:
import bisect
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
A = list(set(A))
A.sort()
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    ml = bisect.bisect_left(A, k) 
    for i in A[:ml]:
        if 2*i == k:
            ans += Ad[i]//2
            del Ad[i]
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            del Ad[i]
            ans += m
        else:
            H[i] = j
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]

H = defaultdict(lambda: [])
N = int(input())
A = inpl()
k = 2**30
ans = 0
for j in range(30,0,-1):
    k = 2**j
    t = []
    H = defaultdict(lambda: [])
    for i in A:
        if H[k-i]:
            t.append(H[k-i].pop())
            t.append(i)
            ans += 1
        else:
            H[i].append(i)
    for p in t:
        A.remove(p)
print(ans)

Fixed submission:
import bisect
from collections import defaultdict
def inpl(): return [int(i) for i in input().split()]
H = defaultdict(lambda: [])
Ad = defaultdict(lambda: 0)
N = int(input())
A = inpl()
for i in A:
    Ad[i] += 1
A = list(set(A))
A.sort()
ans = 0
for j in range(30,0,-1):
    k = 2**j
    H = defaultdict(lambda: [])
    ml = bisect.bisect_left(A, k) 
    for i in A[:ml]:
        if 2*i == k:
            ans += Ad[i]//2
            del Ad[i]
            continue
        if H[k-i]:
            m = min(Ad[k-i], Ad[i])
            Ad[k-i] -= m
            del Ad[i]
            ans += m
        else:
            H[i] = j
print(ans)