<input type="text" name="" id="" class="input" />
<br/><br/><br/><br/>
<input type="submit" value="Buton1" class="buton" />
<input type="submit" value="Buton2" class="buton" />

$(".buton").click(function() {
    var inputDeger = $(".input").val();
	  var deger = $(this).attr("value");
  	$(".input").val(deger);
});