document.writeln('');
var image_number ;
var max_imagenum =11 ;
var image_array =new Array(max_imagenum ) ;
var ram_number ;
var judge_num = 1.0/max_imagenum ;

for(var i=0 ;i <max_imagenum ;i++ ){
	image_array[i] = "img/index_image" + (i+1)+".jpg";
}

ram_number = Math.random() ;
image_number = Math.floor( ram_number/judge_num ) ; 
document.write('<img src="'+image_array[image_number]+'">');