var btn1 = document.getElementById("btn1");
var btn2 = document.getElementById("btn2");
var btn3 = document.getElementById("btn3");
var btn4 = document.getElementById("btn4");
var btn5 = document.getElementById("btn5");
var btn6 = document.getElementById("btn6");
var btn7 = document.getElementById("btn7");
var btn8 = document.getElementById("btn8");
var btn9 = document.getElementById("btn9");
btn5.addEventListener("click", function() {
    var viarableNum=btn1.innerHTML; 
    btn1.innerHTML=btn4.innerHTML; 
    btn4.innerHTML=btn7.innerHTML; 
    btn7.innerHTML=btn8.innerHTML; 
    btn8.innerHTML=btn9.innerHTML; 
    btn9.innerHTML=btn6.innerHTML; 
    btn6.innerHTML=btn3.innerHTML; 
    btn3.innerHTML=btn2.innerHTML; 
    btn2.innerHTML=viarableNum; 
});