function n5_open()
{
    var c=document.getElementById("cvs1").getContext("2d");
    c.beginPath();
    c.fillStyle="#FFFFFF";    c.fillRect(0,0,800,500);
    c.strokeStyle="#000000";
    
    c.moveTo(100,5); c.lineTo(10,100); c.lineTo(200,100); c.lineTo(100,5);
    c.moveTo(50,100); c.lineTo(50,200); c.lineTo(150,200); c.lineTo(150,100);
    c.moveTo(100+30,150);    c.arc(100,150,30,0,Math.PI*2);
    
    c.stroke();
}