var how_many = 4;
var now = new Date()
var sec = now.getSeconds()
var pick = sec % how_many;
pick +=1;
if (pick==1) {
document.write("4")
}

if (pick==2) {
document.write("5")
}

if (pick==3) {
document.write("6")
}

if (pick==4) {
document.write("7")
}