Fair Rations

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;
class Solution {

    static void Main(String[] args) {
        int N = Convert.ToInt32(Console.ReadLine());
        string[] B_temp = Console.ReadLine().Split(' ');
        int[] B = Array.ConvertAll(B_temp,Int32.Parse);
        int oddCount=0,start=-1,end=0,result = 0;
        //List<Vector2> pairs = new List<Vector2>();
        for(int i=0;i<N;i++){
            if(B[i]%2!=0) {
                oddCount++;
                if(start==-1) start = i;
                else{
                    end = i;
                    result += (end-start)*2;
                    start=-1;
                    end=-1;
                }
            }
        }
        if(oddCount%2==0){
            Console.WriteLine(result);
        }else{
            Console.WriteLine("NO");
        }
    }
}