using System;
using System.Collections.Generic;
using System.Text;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            int x;
            for(x=1;x<8;x++)
            {
                int y;
                for(y=1;y<8;y++)
                {
                    if(x == y||x+y==8)
                    {
                        Console.Write("O");
                    }
                    else
                    {
                        Console.Write(".");
                    }
                }
                console.writeLine();
            }//请完善代码
           
        }
    }
}