// create a new array and assign images
var pix = new Array;
pix[0] = "images/photo1.jpg";
pix[1] = "images/photo2.jpg";
pix[2] = "images/photo3.jpg";
pix[3] = "images/photo5.jpg";
pix[4] = "images/photo6.jpg";
pix[5] = "images/photo8.jpg";
pix[6] = "images/photo9.jpg";
pix[7] = "images/photo12.jpg";
pix[8] = "images/photo15.jpg";
pix[9] = "images/photo13.jpg";
pix[10] = "images/photo17.jpg";
pix[11] = "images/photo20.jpg";
pix[12] = "images/photo23.jpg";
pix[13] = "images/photo24.jpg";
pix[14] = "images/photo25.jpg";
pix[15] = "images/photo26.jpg";
pix[16] = "images/photo28.jpg";
pix[17] = "images/photo29.jpg";
pix[18] = "images/photo31.jpg";
pix[19] = "images/photo34.jpg";
pix[20] = "images/photo35.jpg";
pix[21] = "images/photo36.jpg";
pix[22] = "images/photo38.jpg";
pix[23] = "images/photo40.jpg";
pix[24] = "images/photo41.jpg";
pix[25] = "images/photo43.jpg";
pix[26] = "images/photo44.jpg";
pix[27] = "images/photo46.jpg";
pix[28] = "images/photo47.jpg";
pix[29] = "images/photo48.jpg";
pix[30] = "images/photo50.jpg";
pix[31] = "images/photo51.jpg";
pix[32] = "images/photo52.jpg";
pix[33] = "images/photo54.jpg";
pix[34] = "images/photo56.jpg";
pix[35] = "images/photo57.jpg";
pix[36] = "images/photo60.jpg";
pix[37] = "images/photo63.jpg";
pix[38] = "images/photo45.jpg";
pix[39] = "images/photo33.jpg";

// get a random integer between 0 and 39
var rand = Math.floor(Math.random() * 40);

// assign random image to the HTML <img> tag of pic id 
document.getElementById("pich").src = pix[ rand ];