Buggy python submission (verdict: Runtime Error):
n = int(input())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
change_a = [i for i in range(3) if a[i] < b[i]]
change_b = [i for i in range(3) if a[i] > b[i]]
if len(change_a) == 0:
  if len(change_b) == 0:
    print(n)
  elif len(change_b) == 1:
    i = n // b[change_b[0]]
    n = n % b[change_b[0]]
    n += i * a[change_b[0]]
    print(n)
  elif len(change_b) == 2:
    tmp = n
    for i in range(5001):
      m = n
      m -= i * b[change_b[0]]
      if m < 0:
        break
      j = m // b[change_b[1]]
      m = m % b[change_b[1]]
      m += i * a[change_b[0]] + j * a[change_b[1]]
      tmp = max(tmp, m)
    print(tmp)
  else:      
    tmp = n
    for i in range(5001):
      for j in range(5001):
        m = n
        m -= i * b[change_b[0]]
        if m < 0:
          break
        m -= j * b[change_b[1]]
        if m < 0:
          break
        k = m // b[change_b[2]]
        m = m % b[change_b[2]]
        m += i * a[change_b[0]] + j * a[change_b[1]] + k * a[change_b[2]]
        tmp = max(tmp, m)
  print(tmp)
elif len(change_a) == 1:
  i = n // a[change_a[0]]
  n = n % a[change_a[0]]
  n += i * b[change_a[0]]
  if len(change_b) == 0:
    print(n)
  elif len(change_b) == 1:
    i = n // b[change_b[0]]
    n = n % b[change_b[0]]
    n += i * a[change_b[0]]
    print(n)
  elif len(change_b) == 2:
    tmp = n
    for i in range(5001):
      m = n
      m -= i * b[change_b[0]]
      if m < 0:
        break
      j = m // b[change_b[1]]
      m = m % b[change_b[1]]
      m += i * a[change_b[0]] + j * a[change_b[1]]
      tmp = max(tmp, m)
    print(tmp)
elif len(change_a) == 2:
  tmp = n
  for i in range(5001):
    m = n
    m -= i * a[change_a[0]]
    if m < 0:
      break
    j = m // a[change_a[1]]
    m = m % a[change_a[1]]
    m += i * b[change_a[0]] + j * b[change_a[1]]
    tmp = max(tmp, m)
  n = tmp
  if len(change_b) == 0:
    print(n)
  elif len(change_b) == 1:
    i = n // b[change_b[0]]
    n = n % b[change_b[0]]
    n += i * a[change_b[0]]
    print(n)
else:    
  tmp = n
  for i in range(5001):
    for j in range(5001):
      m = n
      m -= i * a[change_a[0]]
      if m < 0:
        break
      m -= j * a[change_a[1]]
      if m < 0:
        break
      k = m // a[change_a[2]]
      m = m % a[change_a[2]]
      m += i * b[change_a[0]] + j * b[change_a[1]] + k * b[change_a[2]]
      tmp = max(tmp, m)
  print(tmp)


Fixed submission:
n = int(input())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
change_a = [i for i in range(3) if a[i] < b[i]]
change_b = [i for i in range(3) if a[i] > b[i]]
if len(change_a) == 0:
  if len(change_b) == 0:
    print(n)
  elif len(change_b) == 1:
    i = n // b[change_b[0]]
    n = n % b[change_b[0]]
    n += i * a[change_b[0]]
    print(n)
  elif len(change_b) == 2:
    tmp = n
    for i in range(5001):
      m = n
      m -= i * b[change_b[0]]
      if m < 0:
        break
      j = m // b[change_b[1]]
      m = m % b[change_b[1]]
      m += i * a[change_b[0]] + j * a[change_b[1]]
      tmp = max(tmp, m)
    print(tmp)
  else:      
    tmp = n
    for i in range(5001):
      for j in range(5001):
        m = n
        m -= i * b[change_b[0]]
        if m < 0:
          break
        m -= j * b[change_b[1]]
        if m < 0:
          break
        k = m // b[change_b[2]]
        m = m % b[change_b[2]]
        m += i * a[change_b[0]] + j * a[change_b[1]] + k * a[change_b[2]]
        tmp = max(tmp, m)
    print(tmp)
elif len(change_a) == 1:
  i = n // a[change_a[0]]
  n = n % a[change_a[0]]
  n += i * b[change_a[0]]
  if len(change_b) == 0:
    print(n)
  elif len(change_b) == 1:
    i = n // b[change_b[0]]
    n = n % b[change_b[0]]
    n += i * a[change_b[0]]
    print(n)
  elif len(change_b) == 2:
    tmp = n
    for i in range(n // b[change_b[0]] + 1):
      m = n
      m -= i * b[change_b[0]]
      if m < 0:
        break
      j = m // b[change_b[1]]
      m = m % b[change_b[1]]
      m += i * a[change_b[0]] + j * a[change_b[1]]
      tmp = max(tmp, m)
    print(tmp)
elif len(change_a) == 2:
  tmp = n
  for i in range(5001):
    m = n
    m -= i * a[change_a[0]]
    if m < 0:
      break
    j = m // a[change_a[1]]
    m = m % a[change_a[1]]
    m += i * b[change_a[0]] + j * b[change_a[1]]
    tmp = max(tmp, m)
  n = tmp
  if len(change_b) == 0:
    print(n)
  elif len(change_b) == 1:
    i = n // b[change_b[0]]
    n = n % b[change_b[0]]
    n += i * a[change_b[0]]
    print(n)
else:    
  tmp = n
  for i in range(5001):
    for j in range(5001):
      m = n
      m -= i * a[change_a[0]]
      if m < 0:
        break
      m -= j * a[change_a[1]]
      if m < 0:
        break
      k = m // a[change_a[2]]
      m = m % a[change_a[2]]
      m += i * b[change_a[0]] + j * b[change_a[1]] + k * b[change_a[2]]
      tmp = max(tmp, m)
  print(tmp)