Buggy python submission (verdict: Time Limit Exceeded):
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    for j in range(1,50):
      d=2**j
      if A[-1-i]<d:
        e=d-A[-1-i]
        break
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)


Fixed submission:
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    d=A[-1-i]
    f=len(bin(d))-2
    e=2**f-d
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    for j in range(1,16):
      d=2**j
      if A[-1-i]<d:
        e=d-A[-1-i]
        break
    if e in D:
      if D[e]>0:
        cnt+=1
        D[e]-=1
print(cnt)

Fixed submission:
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    d=A[-1-i]
    f=len(bin(d))-2
    e=2**f-d
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    for j in range(1,16):
      d=2**j
      if A[-1-i]<d:
        e=d-A[-1-i]
        break
    if e in D:
      cnt+=1
      D[e]-=1
print(cnt)

Fixed submission:
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    d=A[-1-i]
    f=len(bin(d))-2
    e=2**f-d
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    for j in range(1,16):
      d=2**j
      if A[-1-i]<d:
        e=d-A[-1-i]
        break
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)

Fixed submission:
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    d=A[-1-i]
    f=len(bin(d))-2
    e=2**f-d
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    for j in range(1,16):
      d=2**j
      if A[-1-i]<d:
        e=d-A[-1-i]
        break
    if D[e]>0:
      cnt+=1
      D[A[-1-i]]-=1
      D[e]-=1
print(cnt)
         

Fixed submission:
N=int(input())
A=list(map(int,input().split()))
A=sorted(A)
from collections import Counter as co
D=co(A)

cnt=0
for i in range(N):
  if D[A[-1-i]]>0:
    D[A[-1-i]]-=1
    d=A[-1-i]
    f=len(bin(d))-2
    e=2**f-d
    if D[e]>0:
      cnt+=1
      D[e]-=1
print(cnt)