Problem:
Score : 400 points

Problem Statement

Snuke has N strings. The i-th string is s_i.

Let us concatenate these strings into one string after arranging them in some order.
Find the maximum possible number of occurrences of AB in the resulting string.

Constraints

1 \leq N \leq 10^{4}

2 \leq |s_i| \leq 10

s_i consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

N
s_1
\vdots
s_N

Output

Print the answer.

Sample Input 1

3
ABCA
XBAZ
BAD

Sample Output 1

2

For example, if we concatenate ABCA, BAD and XBAZ in this order, the resulting string ABCABADXBAZ has two occurrences of AB.

Sample Input 2

9
BEWPVCRWH
ZZNQYIJX
BAVREA
PA
HJMYITEOX
BCJHMRMNK
BP
QVFABZ
PRGKSPUNA

Sample Output 2

4

Sample Input 3

7
RABYBBE
JOZ
BMHQUVA
BPA
ISU
MCMABAOBHZ
SZMEHMA

Sample Output 3

4

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using static System.Math;

namespace _20190511
{
    class Program
    {
        public static void Main(string[] args)
        {
            using (var sc = new SetConsole())
            {
                int count = 0;
                int n = GetString().ToInt();
                var list = new List<string>();
                var a = new Stack<string>();
                var b = new Stack<string>();
                var ab = new List<string>();
                for (int i = 0; i < n; i++)
                {
                    var str = GetString();
                    if ('A' == str[str.Length - 1] && 'B' == str[0])
                    {
                        ab.Add(str);
                    }
                    else if ('A' == str[str.Length - 1])
                    {
                        a.Push(str);
                    }
                    else if ('B' == str[0])
                    {
                        b.Push(str);
                    }
                    
                    for (int j = 0; j < str.Length - 1; j++)
                    {
                        if ('A' == str[j] && 'B' == str[j+1])
                        {
                            count++;
                        }
                    }
                }

                int abCount = ab.Count - 1 > 0 ? ab.Count - 1 : 0;
                count += ab.Count - 1;
                if (abCount > 0)
                {
                    if (a.Any())
                    {
                        a.Pop();
                        count++;
                    }
                    if (b.Any())
                    {
                        b.Pop();
                        count++;
                    }
                }
                
                count += Min(a.Count, b.Count);
                CWrite(count);                
            }
        }

        static void CWrite<T>(T str) => Console.WriteLine(str);
        static string GetString() => Console.ReadLine();
        static T[] GetArray<T>()
        {
            var t = typeof(T);
            var str = Console.ReadLine();
            if (t == typeof(string))
            {
                return (T[])(object)str.Split();
            }
            if (t == typeof(int))
            {
                return (T[])(object)str.ToNumArray<T>();
            }
            if (t == typeof(long))
            {
                return (T[])(object)str.ToNumArray<T>();
            }
            if (t == typeof(double))
            {
                return (T[])(object)str.ToNumArray<T>();
            }
            throw new NotSupportedException($"{t} is not supported.");
        }
    }



    class SetConsole : IDisposable
    {
        readonly StreamWriter sw = new StreamWriter(Console.OpenStandardOutput());
        public SetConsole()
        {
            sw.AutoFlush = false;
            Console.SetOut(sw);
        }
        public void Dispose()
        {
            Console.Out.Flush();
            sw.AutoFlush = true;
            Console.SetOut(sw);
        }
    }

    static class ExtentionsLibrary
    {
        public static T[] ToNumArray<T>(this string str)
        {
            var t = typeof(T);
            if (t == typeof(int))
            {
                return (T[])(object)str.Split().Select(int.Parse).ToArray();
            }
            if (t == typeof(long))
            {
                return (T[])(object)str.Split().Select(long.Parse).ToArray();
            }
            if (t == typeof(double))
            {
                return (T[])(object)str.Split().Select(double.Parse).ToArray();
            }
            throw new NotSupportedException();
        }
        public static int ToInt(this string str) => int.Parse(str);
    }
}