Edit in JSFiddle

$("#but0,#but1, #but2,#but3,#but4,#but5").on('click', firstClick)

function firstClick() {
    alert("First Clicked");
    $("#but0,#but1, #but2,#but3,#but4,#but5").off('click').on('click', secondClick)
}

function secondClick() {
    alert("Second Clicked");
    $("#but0,#but1, #but2,#but3,#but4,#but5").off('click').on('click', firstClick)
}

<input type="button" id="but0" value="Click Me" />
<input type="button" id="but1" value="Click Me" />
<input type="button" id="but2" value="Click Me" />
<input type="button" id="but3" value="Click Me" />
<input type="button" id="but4" value="Click Me" />
<input type="button" id="but5" value="Click Me" />

#but0,#but1, #but2,#but3,#but4,#but5{
height: 85%;
width: 30.4%;
margin: 1%;
position: relative;
border-radius: 10px;
border:solid 2px #fff;
color: white;
font-size: 25px;
background-color:#9DA2A5; 
}