Buggy python submission (verdict: Time Limit Exceeded):
import math
n=int(input())
A=[int(i) for i in input().split()]
A.sort(reverse=True)
B=[]
for a in A:
  B.append(a)
count=0
for i in range(n):
  cur=A[i]
  if cur in B:
    B=B[1:]
    k=int(math.log2(cur))+1
    pair=2**k-cur
    if pair in B:
      B.remove(pair)
      count+=1
print(count)


Fixed submission:
import bisect
import collections
def f(n):
  return n.bit_length()
n=int(input())
A=[int(i) for i in input().split()]
D=dict(collections.Counter(A))
C=sorted(list(D.keys()))
ans=0
for i in range(len(C)):
  pair=2**f(C[-(i+1)])-C[-(i+1)]
  k=bisect.bisect_left(C,pair)
  if C[k]==pair:
    if k==len(C)-(i+1):
      ans+=D[pair]//2
      D[pair]%=2
    else:
      aa=min(D[pair],D[C[-(i+1)]])
      ans+=aa
      D[pair]-=aa
      D[C[-(i+1)]]-=aa
print(ans)

Buggy python submission (verdict: Runtime Error):
import math
n=int(input())
A=[int(i) for i in input().split()]
B=[]
for a in A:
  B.append(a)
A.sort(reverse=True)
count=0
for i in range(n):
  cur=A[i]
  if cur in B:
    k=int(math.log2(cur))+1
    pair=2**k-cur
    if pair in B:
      B.remove(pair)
      B.remove(cur)
      count+=1
print(count)


Fixed submission:
import bisect
import collections
def f(n):
  return n.bit_length()
n=int(input())
A=[int(i) for i in input().split()]
D=dict(collections.Counter(A))
C=sorted(list(D.keys()))
ans=0
for i in range(len(C)):
  pair=2**f(C[-(i+1)])-C[-(i+1)]
  k=bisect.bisect_left(C,pair)
  if C[k]==pair:
    if k==len(C)-(i+1):
      ans+=D[pair]//2
      D[pair]%=2
    else:
      aa=min(D[pair],D[C[-(i+1)]])
      ans+=aa
      D[pair]-=aa
      D[C[-(i+1)]]-=aa
print(ans)

Buggy python submission (verdict: Runtime Error):
import math
n=int(input())
A=[int(i) for i in input().split()]
B=[]
for a in A:
  B.append(a)
A.sort(reverse=True)
count=0
for i in range(n):
  cur=A[i]
  if cur in B:
    k=int(math.log2(cur))+1
    pair=2**k-cur
    if pair in B:
      B.remove(pair)
      count+=1
print(count)

Fixed submission:
import bisect
import collections
def f(n):
  return n.bit_length()
n=int(input())
A=[int(i) for i in input().split()]
D=dict(collections.Counter(A))
C=sorted(list(D.keys()))
ans=0
for i in range(len(C)):
  pair=2**f(C[-(i+1)])-C[-(i+1)]
  k=bisect.bisect_left(C,pair)
  if C[k]==pair:
    if k==len(C)-(i+1):
      ans+=D[pair]//2
      D[pair]%=2
    else:
      aa=min(D[pair],D[C[-(i+1)]])
      ans+=aa
      D[pair]-=aa
      D[C[-(i+1)]]-=aa
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import math
n=int(input())
A=[int(i) for i in input().split()]
B=[]
for a in A:
  B.append(a)
A.sort(reverse=True)
count=0
for i in range(n):
  cur=A[i]
  if cur in B:
    B.remove(cur)
    k=int(math.log2(cur))+1
    pair=2**k-cur
    if pair in B:
      B.remove(pair)
      count+=1
print(count)

Fixed submission:
import bisect
import collections
def f(n):
  return n.bit_length()
n=int(input())
A=[int(i) for i in input().split()]
D=dict(collections.Counter(A))
C=sorted(list(D.keys()))
ans=0
for i in range(len(C)):
  pair=2**f(C[-(i+1)])-C[-(i+1)]
  k=bisect.bisect_left(C,pair)
  if C[k]==pair:
    if k==len(C)-(i+1):
      ans+=D[pair]//2
      D[pair]%=2
    else:
      aa=min(D[pair],D[C[-(i+1)]])
      ans+=aa
      D[pair]-=aa
      D[C[-(i+1)]]-=aa
print(ans)