My code is saying there are syntax errors where i am unable to find them… can someone help me please?

it is saying line 3 mainly. I really am confused, seeing as im a beginer that is expected, but i could really use some help because this is for my schools coding team, and I will get yelled at >:(

   <html>
     <head>
         <title>Javascript Stuff</title>
       </head>  

   <body>
    
   <script>
var input=prompt("Enter a number:");
if input> 0 {
    alert("negative")
}
else (input < 0)
   alert("Zero");
if else{ 
   alert("Positive");
}
    </script>
    </body>
                
                </html>