function plus(){
 document.getElementById('metres').value++;
 var metres=document.getElementById('metres').value;
 recount(); 
} 

function minus(){
 if (document.getElementById('metres').value>1) document.getElementById('metres').value--;
 var metres=document.getElementById('metres').value;         
 recount(); 
}

function recount(){
 var price=document.getElementById('metres').value*15;
 document.getElementById('result').innerHTML=price;
 var dlina=document.getElementById('metres').value.length;
 var newdlina=(dlina*10)+'px';
 document.getElementById('metres').style.width=newdlina;
}

function clearinp(){
 document.getElementById('metres').value='';
}

function checkinpt(){
 if (document.getElementById('metres').value=='') document.getElementById('metres').value=1;
 var dlina=document.getElementById('metres').value.length;
 var newdlina=(dlina*10)+'px';
 document.getElementById('metres').style.width=newdlina;  
}   

function precount(){
 var price=document.getElementById('metres').value*15;
 document.getElementById('result').innerHTML=price;
 var dlina=document.getElementById('metres').value.length+1;
 var newdlina=(dlina*10)+'px';
 document.getElementById('metres').style.width=newdlina;  
  
}