function liczonko(){
var x= document.getElementById('put_in').value;
if(x=="1"){
document.write("jeden");
}
}
<!DOCTYPE html>
<html lang="pl">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script type=”text/javascript” src=”licz.js”></script>
<title>Document</title>
</head>
<body >
<input type="number" name="nazwa" min="0" max="100" id="put_in">
<input type="submit" value="Submit" onclick="liczonko()">
<div class="box"></div>
</body>
</html>
.box{
position:absolute;
top:20vh;
width:10%;
height:20vh;
background:black;
color:white;
}