using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    static class Program
    {
        /// <summary>
        /// アプリケーションのメイン エントリ ポイントです。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Form[] forms = new Form[3];

            for (int i = 0; i < forms.Length; ++i)
            {
                forms[i] = new Form();
                forms[i].FormClosed += (sender, e) => {
                    int count = 0;
                    foreach (Form f in forms)
                    {
                        if (f.Visible == false) count++;
                    }
                    if (count == 2)
                        Application.Exit();
                };
                forms[i].Show();
            }

            Application.Run();
        }
    }
}