 
  
  <!DOCTYPE html>
<html lang='ru'>
<head>
	<meta charset="UTF-8">
	<title></title>
	<style>
		#clicker{
			height: 200px;
			width: 400px;
		}
		#count{
			font-size: 400%;
		}
	</style>
</head>
<body>
	<button id="clicker">click</button>
	<div id="count">o</div>
	<button id="save">начало пути  </button>
	<span id="saving"></span>
	<br><br>
	<button id="save2">конец пути  </button>
	<span id="saving2"></span>
	<br><br>
		<button id="send">сколько я прошёл</button>
		<span id="sendOTVET">-</span>
</body>
</html>
<script>
	var count = 0;
	function a() {
		count+= 1;
		document.getElementById('count').innerHTML = count;
	}
	clicker.addEventListener('mousedown' , a);
	clicker.addEventListener('contextmenu' , a);
	save.addEventListener('click' , function () {
		document.getElementById('saving').innerHTML = count;
	});
	save2.addEventListener('click' , function () {
		document.getElementById('saving2').innerHTML = count;
	});
	var saving = Number(document.getElementById('saving').innerText);
	var saving2 = Number(document.getElementById('saving2').innerText);
	send.addEventListener('click' , function () {
		document.getElementById('sendOTVET').innerHTML = saving2 - saving;
	});
</script> 
  
  send.addEventListener('click' , function () {
    var saving = Number(document.getElementById('saving').innerText);
    var saving2 = Number(document.getElementById('saving2').innerText);
    document.getElementById('sendOTVET').innerHTML = saving2 - saving;
  });send.addEventListener('click' , function () {
  var saving = Number(document.getElementById('saving').innerText);
  var saving2 = Number(document.getElementById('saving2').innerText);
  document.getElementById('sendOTVET').innerHTML = saving2 - saving;
});clicker.addEventListener('mousedown' , a);document.getElementById("clicker").addEventListener('mousedown' , a);