The Smart Beaver from ABBYY got hooked on square matrices. Now he is busy studying an n × n size matrix, where n is odd. The Smart Beaver considers the following matrix elements good: 

  * Elements of the main diagonal. 
  * Elements of the secondary diagonal. 
  * Elements of the "middle" row — the row which has exactly <image> rows above it and the same number of rows below it. 
  * Elements of the "middle" column — the column that has exactly <image> columns to the left of it and the same number of columns to the right of it. 

<image> The figure shows a 5 × 5 matrix. The good elements are marked with green. 

Help the Smart Beaver count the sum of good elements of the given matrix.

Input

The first line of input data contains a single odd integer n. Each of the next n lines contains n integers aij (0 ≤ aij ≤ 100) separated by single spaces — the elements of the given matrix.

The input limitations for getting 30 points are: 

  * 1 ≤ n ≤ 5



The input limitations for getting 100 points are:

  * 1 ≤ n ≤ 101

Output

Print a single integer — the sum of good matrix elements.

Examples

Input

3
1 2 3
4 5 6
7 8 9


Output

45


Input

5
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1


Output

17

Note

In the first sample all matrix elements will be good. Good elements in the second sample are shown on the figure.
""" Python 3 compatibility tools. """
from __future__ import division, print_function
import itertools
import sys
import os
from io import BytesIO, IOBase


if sys.version_info[0] < 3:
  input = raw_input
  range = xrange

  filter = itertools.ifilter
  map = itertools.imap
  zip = itertools.izip


def is_it_local():
  script_dir = str(os.getcwd()).split('/')
  username = "dipta007"
  return username in script_dir


def READ(fileName):
  if is_it_local():
    sys.stdin = open(f'./{fileName}', 'r')

# region fastio
BUFSIZE = 8192

class FastIO(IOBase):
  newlines = 0

  def __init__(self, file):
    self._fd = file.fileno()
    self.buffer = BytesIO()
    self.writable = "x" in file.mode or "r" not in file.mode
    self.write = self.buffer.write if self.writable else None

  def read(self):
    while True:
      b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
      if not b:
          break
      ptr = self.buffer.tell()
      self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
    self.newlines = 0
    return self.buffer.read()

  def readline(self):
    while self.newlines == 0:
      b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
      self.newlines = b.count(b"\n") + (not b)
      ptr = self.buffer.tell()
      self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
    self.newlines -= 1
    return self.buffer.readline()

  def flush(self):
    if self.writable:
      os.write(self._fd, self.buffer.getvalue())
      self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
  def __init__(self, file):
    self.buffer = FastIO(file)
    self.flush = self.buffer.flush
    self.writable = self.buffer.writable
    self.write = lambda s: self.buffer.write(s.encode("ascii"))
    self.read = lambda: self.buffer.read().decode("ascii")
    self.readline = lambda: self.buffer.readline().decode("ascii")

if not is_it_local():
  sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
  input = lambda: sys.stdin.readline().rstrip("\r\n")

# endregion


def input1(type=int):
  return type(input())


def input2(type=int):
  [a, b] = list(map(type, input().split()))
  return a, b


def input3(type=int):
  [a, b, c] = list(map(type, input().split()))
  return a, b, c


def input_array(type=int):
  return list(map(type, input().split()))


def input_string():
  s = input()
  return list(s)

##############################################################

def main():
  n = input1()
  arr = []
  for i in range(n):
    now = input_array()
    arr.append(now)
  
  r = 0
  c = 0
  res = 0
  while r < n and c < n:
    res += arr[r][c]
    arr[r][c] = 0
    r += 1
    c += 1
  
  r = 0
  c = n-1
  while r < n and c >= 0:
    res += arr[r][c]
    arr[r][c] = 0
    r += 1
    c -= 1
  
  for i in range(n):
    res += arr[n//2][i]
    arr[n//2][i] = 0

  for i in range(n):
    res += arr[i][n//2]
    arr[i][n//2] = 0

  print(res)
  pass

if __name__ == '__main__':
  # READ('in.txt')
  main()