function check(ad)
{
	var ch=ad.value;
	if(isNaN(ch))
	{
		var df=ch.substring(0,(ch.length-1))
		ad.value=df;
	}	
}



function bin()
{
	var a=parseInt(document.bi.n.value);
	var b=parseInt(document.bi.r.value);
	var c=parseFloat(document.bi.p.value);
	if(c>1)
	{
		alert("The probability of success must be between 0 and 1");
	}
	else if(b>a)
	{
		alert("Number of success r should be less than number of events n");
	}
	else
	{
		
//n!
		var z=1;
		for(var i=a; i>=1; i--)
		{
			z=z*i;
			
		}

//r!
		var x=1;
		for(var k=b;k>=1;k--)
		{
			x=x*k;
		}

//(n-r)!
		var s=a-b;
		var t=1;
		for(var j=s;j>=1;j--)
		{
			t=t*j;
		}	

//PERMUTATION [ n!/(n-r)! ]
		var p=z/t;

//COMBINATION [ (n!/(n-r)!) / r! ] , nCr = y ; 1-p = d ; n-r = e ; p^r=f 
		var y=p/x;
		var d=1-c;
		var e=a-b;
		var f=Math.pow(c,b);
		var g=Math.pow(d,e);
		
//BINOMIAL DISTRIBUTION
		var res=y*f*g;
		document.bi.b.value=Math.round((res)*1000)/1000;
	}	
}