please help its urgent,on click of generatePDF button on opportunity ,I am trying to display the fields of  account and its contacts(not opportunities of only contact) of that oportunity on the pdf page,I am able to display record of account related to opportunity,but i  am not able to get and display that accounts related contacts.Please help me in this scenario.below is code.

Unable to query the contacts of account of the opportunity(please help)

Controller:
--------------
public with sharing class diplayacccontofopp {
public list<opportunity> opp{set;get;}
public list<contact> oppcon{set;get;}
public list<contact> con{set;get;}
public list<account> acc{set;get;}

    public diplayacccontofopp(ApexPages.StandardController controller) {
    Id OppotunityIDs = ApexPages.currentPage().getParameters().get('Id');
    map<id,account> mo=new map<id,account>([select id,name  From account]);  
        
        
       // opp=[select id, name,account.id,account.name from opportunity where id =:OppotunityIDs ];
       //acc= [select id,Name,(select id,FirstName,LastName FROM Contacts ) From Account where id =:opp[0].id];
       
    opp = [select id,AccountId,account.id,account.name  From Opportunity WHERE Id=:OppotunityIDs ];
    acc=[select id, Name,(Select name,id From Opportunities where id=:OppotunityIDs) from Account ];
    
 oppcon=[SELECT Id, Name,firstname FROM contact where accountId=:acc[0].id];   
    }

}

VF page:
---------------
<apex:page standardController="opportunity" extensions="diplayacccontofopp" renderAs="PDF">
<table width="100%" style="font-family: Arial, Helvetica, sans-serif; border-collapse: collapse;"
        cellpadding="5">
        <tr>
            <td colspan="4" style="font-size: x-large;">
                Opportunity Info
            </td>
        </tr>
        <tr>
            <td colspan="2" >
                {!Opportunity.Name}
            </td>
        </tr>
        <tr>
            <td colspan="15">
            </td>
        </tr>
        
        <tr>
            <td colspan="4" style="font-size: x-large;">
            ACCOUNT INFO
            </td>
        </tr>
        
        <apex:repeat value="{!opp}" var="op">
                <tr id="{!op.account.Id}">
                    <td>
                        {!op.account.name}
                    </td>
                </tr>            
        </apex:repeat>
        
        
      
          
            
       </table>
       
            
    <!--<table>
  <apex:repeat value="{!acc}" var="a">
    <tr>
      <td></td>
      <apex:repeat value="{!a.Contacts}" var="cont">
         <td><apex:outputText value="{!cont.firstName}"/></td>
      </apex:repeat>
    </tr>
  </apex:repeat>
  
</table>-->
       
    <table>   
   <apex:repeat value="{!oppcon}" var="a">
    <tr>
      <td></td>
      <apex:repeat value="{!a.Id}" var="cont">
         <td><apex:outputText value="{!a.firstname}"/></td>
      </apex:repeat>
    </tr>
  </apex:repeat>
            </table>


</apex:page>

Thanks,
B.Mahanandeesh.