There are n armchairs, numbered from 1 to n from left to right. Some armchairs are occupied by people (at most one person per armchair), others are not. The number of occupied armchairs is not greater than n/2.

For some reason, you would like to tell people to move from their armchairs to some other ones. If the i-th armchair is occupied by someone and the j-th armchair is not, you can tell the person sitting in the i-th armchair to move to the j-th armchair. The time it takes a person to move from the i-th armchair to the j-th one is |i - j| minutes. You may perform this operation any number of times, but these operations must be done sequentially, i. e. you cannot tell a person to move until the person you asked to move in the last operation has finished moving to their destination armchair.

You want to achieve the following situation: every seat that was initially occupied must be free. What is the minimum time you need to do it?

Input

The first line contains one integer n (2 ≤ n ≤ 5000) — the number of armchairs.

The second line contains n integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ 1). a_i = 1 means that the i-th armchair is initially occupied, a_i = 0 means that it is initially free. The number of occupied armchairs is at most n/2.

Output

Print one integer — the minimum number of minutes you have to spend to achieve the following situation: every seat that was initially occupied must be free.

Examples

Input


7
1 0 0 1 0 0 1


Output


3


Input


6
1 1 1 0 0 0


Output


9


Input


5
0 0 0 0 0


Output


0

Note

In the first test, you can perform the following sequence:

  1. ask a person to move from armchair 1 to armchair 2, it takes 1 minute; 
  2. ask a person to move from armchair 7 to armchair 6, it takes 1 minute; 
  3. ask a person to move from armchair 4 to armchair 5, it takes 1 minute. 



In the second test, you can perform the following sequence:

  1. ask a person to move from armchair 1 to armchair 4, it takes 3 minutes; 
  2. ask a person to move from armchair 2 to armchair 6, it takes 4 minutes; 
  3. ask a person to move from armchair 4 to armchair 5, it takes 1 minute; 
  4. ask a person to move from armchair 3 to armchair 4, it takes 1 minute. 



In the third test, no seat is occupied so your goal is achieved instantly.
"""
// Author : snape_here - Susanta Mukherjee
     
 """

from __future__ import division, print_function
 
import os,sys
from io import BytesIO, IOBase
 
if sys.version_info[0] < 3:
    from __builtin__ import xrange as range
    from future_builtins import ascii, filter, hex, map, oct, zip
 
def ii(): return int(input())
def fi(): return float(input())
def si(): return input()
def msi(): return map(str,input().split())
def mi(): return map(int,input().split())
def li(): return list(mi())
def lsi(): return list(msi())
 
def read():
    sys.stdin = open('input.txt', 'r')  
    sys.stdout = open('output.txt', 'w') 
 
def gcd(x, y):
    while y:
        x, y = y, x % y
    return x

def lcm(x, y):
    return (x*y)//(gcd(x,y))

mod=1000000007

def modInverse(b,m): 
    g = gcd(b, m)  
    if (g != 1):         
        return -1
    else:          
        return pow(b, m - 2, m) 

def ceil2(x,y):
    if x%y==0:
        return x//y
    else:
        return x//y+1

def modu(a,b,m): 

    a = a % m 
    inv = modInverse(b,m) 
    if(inv == -1): 
        return -999999999
    else: 
        return (inv*a)%m

from math import log,factorial,cos,tan,sin,radians,floor,sqrt,ceil

import bisect
import random
import string 

from decimal import *

getcontext().prec = 50

abc="abcdefghijklmnopqrstuvwxyz"

pi=3.141592653589793238

def gcd1(a):

    if len(a) == 1:
        return a[0]

    ans = a[0]
    for i in range(1,len(a)):
        ans = gcd(ans,a[i])

    return ans

def mykey(x):
    return len(x)

def checkper_sq(n):
    def check(n,mod):
        for i in range(mod):
            if (i*i)%mod == n%mod:
                return True 
        return False
    for i in range(3,101):
        if not check(n,i):
            return False 
    return True

def main():

    for _ in range(1):
        n=ii()
        a=li()
        arr=[]
        v=[0 for i in range(n)]
        k=0
        for i in range(n):
            if a[i]==1:
                arr.append(i)
                v[i]=1
                k+=1
        dp=[[10**18 for i in range(k+1)]for j in range(n+1)]
        for i in range(n+1):
            dp[i][0]=0
        for i in range(1,n+1):
            for j in range(1,k+1):
                dp[i][j]=dp[i-1][j]
            if v[i-1]==1:
                continue
            for j in range(1,k+1):
                dp[i][j]=min(dp[i][j],dp[i-1][j-1]+abs(i-1-arr[j-1]))
        print(dp[-1][-1])

# 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")
 
 
def print(*args, **kwargs):
    """Prints the values to a stream, or to sys.stdout by default."""
    sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
    at_start = True
    for x in args:
        if not at_start:
            file.write(sep)
        file.write(str(x))
        at_start = False
    file.write(kwargs.pop("end", "\n"))
    if kwargs.pop("flush", False):
        file.flush()
 
 
if sys.version_info[0] < 3:
    sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
else:
    sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
 
input = lambda: sys.stdin.readline().rstrip("\r\n")
 
# endregion

 
if __name__ == "__main__":
    #read()
    main()