// JavaScript Document
function factorial(n){
	var result=1;
	for(var i=1;i<=n;i++)
		result*=i;
	return result;
}

function arrange(m,n){					//m is the total numbers,n is 7.
	var result=1;
	for(var i=m;i>=m-n+1;i--)
		result*=i;
	return result;
}

function compose(m,n){
	if(m>=n)
		return arrange(m,n)/factorial(n);
}



function setbettype(){

  switch(tz.bettype.value){
   case '1':
     singlenum.style.display=''
	 composenum.style.display='none'
	 couragenum.style.display='none'
	 groupnum.style.display='none'
	 tz.account.value=''
	 break
   case '2':
     singlenum.style.display='none'
	 composenum.style.display=''
	 couragenum.style.display='none'
	 groupnum.style.display='none'
	 tz.account.value=''
	 break	
   case '3':
     singlenum.style.display='none'
	 composenum.style.display='none'
	 couragenum.style.display=''
	 groupnum.style.display=''
	 tz.account.value=''
	 break
   default:
     document.writeln(tz.bettype.value)
	 break
  }
  	 	 	 	 
}

function calculateMoney(){

  switch(tz.bettype.value){
   case '1':
     tz.account.value=tz.singlen.value*2;
	 break
   case '2':
     if (tz.composen.value<8)
       alert("复式个数应该大于7");
     else
		 	 tz.account.value=compose(tz.composen.value,7)*2;
	 break	
   case '3':
   	 if ((tz.couragen.value>6)||(tz.couragen.value<1))
   	   alert("胆码个数范围1--6");
		 else
		   tz.account.value=compose(tz.groupn.value,7-tz.couragen.value)*2;
	 break
   default:
     document.writeln(tz.bettype.value)
	 break
  }
  	 	 	 	 
}