Language: C++

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace divertaPCBX
{
    class Program
    {
        static void Main(string[] args)
        {
            int AB = 0;
            int BA = 0;
            int BX = 0;
            int XA = 0;
            int N = int.Parse(Console.ReadLine());
            string[] s = new string[N];
            for (int i = 0; i < N; i++)
            {
                s[i] = Console.ReadLine();

                while (s[i].IndexOf("AB") > -1)
                {
                    AB++;//"AB"
                    s[i] = s[i].Remove(s[i].IndexOf("AB"), 2);
                }

                if (s[i].Substring(0, 1) == "B")
                {
                    if (s[i].Substring(s[i].Length - 1, 1) == "A")
                    {
                        BA++;//"BA"
                    }
                    else
                    {
                        BX++;//"BX"
                    }
                }
                else if (s[i].Substring(s[i].Length - 1, 1) == "A")
                {
                    XA++;//"XA"
                }
            }
            //
            int ans = 0;
            if (XA==0)
            {
                ans = AB + Math.Min(BA, BX);
            }
            else
            {
                if (BA>0&&BX==0)
                {
                    ans = AB+BA;
                }
                if (BA>0&&BX>0)
                {
                    ans = AB + BA + 1 + Math.Min(XA - 1, BX - 1);
                }
                if (BA==0&&BX>0)
                {
                    ans = AB + Math.Min(XA, BX);
                }
                if (BA == 0 && BX == 0)
                {
                    ans = AB;
                }
            }
            Console.WriteLine(ans);

        }
    }
}


Compiler output:
a.cc:1:7: error: expected nested-name-specifier before 'System'
    1 | using System;
      |       ^~~~~~
a.cc:2:7: error: expected nested-name-specifier before 'System'
    2 | using System.Collections.Generic;
      |       ^~~~~~
a.cc:3:7: error: expected nested-name-specifier before 'System'
    3 | using System.Linq;
      |       ^~~~~~
a.cc:4:7: error: expected nested-name-specifier before 'System'
    4 | using System.Text;
      |       ^~~~~~
a.cc:5:7: error: expected nested-name-specifier before 'System'
    5 | using System.Threading.Tasks;
      |       ^~~~~~
a.cc:11:26: error: 'string' has not been declared
   11 |         static void Main(string[] args)
      |                          ^~~~~~
a.cc:11:35: error: expected ',' or '...' before 'args'
   11 |         static void Main(string[] args)
      |                                   ^~~~
a.cc:73:6: error: expected ';' after class definition
   73 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void divertaPCBX::Program::Main(int*)':
a.cc:17:21: error: expected primary-expression before 'int'
   17 |             int N = int.Parse(Console.ReadLine());
      |                     ^~~
a.cc:18:13: error: 'string' was not declared in this scope
   18 |             string[] s = new string[N];
      |             ^~~~~~
a.cc:18:20: error: expected primary-expression before ']' token
   18 |             string[] s = new string[N];
      |                    ^
a.cc:21:17: error: 's' was not declared in this scope
   21 |                 s[i] = Console.ReadLine();
      |                 ^
a.cc:21:24: error: 'Console' was not declared in this scope
   21 |                 s[i] = Console.ReadLine();
      |                        ^~~~~~~
a.cc:49:28: error: 'Math' was not declared in this scope
   49 |                 ans = AB + Math.Min(BA, BX);
      |                            ^~~~
a.cc:59:41: error: 'Math' was not declared in this scope
   59 |                     ans = AB + BA + 1 + Math.Min(XA - 1, BX - 1);
      |                                         ^~~~
a.cc:63:32: error: 'Math' was not declared in this scope
   63 |                     ans = AB + Math.Min(XA, BX);
      |                                ^~~~
a.cc:70:13: error: 'Console' was not declared in this scope
   70 |             Console.WriteLine(ans);
      |             ^~~~~~~