function processFactorial() {
var n = document.factorialForm.input.value;
	try
		{
 		var value = factorial(parseInt(n),1);
		}
	catch (error)
		{
 		 document.getElementById("factorialAnswer").innerHTML = "You must enter a positive integer first. Try again.";
		}

if ((n == '')|| (parseInt(n) < 0) || (Math.floor(n) != n)) document.getElementById("factorialAnswer").innerHTML = "You must enter a positive integer. Try again.";
else document.getElementById("factorialAnswer").innerHTML =  n.toString() + "! = " + value;
}

function processPermutation() {

var n = document.permutationForm.inputN.value;
var r = document.permutationForm.inputR.value;

	try
		{
 		var value = nPr(parseInt(n), parseInt(r));
		}
	catch (error)
		{
 		 document.getElementById("permutationAnswer").innerHTML = "You must enter two positive integers first. Try again.";
		}


if ((n == '')|| (parseInt(n) < 0) || (Math.floor(n) != n)) document.getElementById("permutationAnswer").innerHTML = "<font class = math>n</font> must be a positive integer. Try again.";
else if ((r == '')|| (parseInt(r) < 0) || (Math.floor(r) != r)) document.getElementById("permutationAnswer").innerHTML = "<font class = math>r</font> must be a positive integer. Try again.";
else if (parseInt(n) < parseInt(r)) document.getElementById("permutationAnswer").innerHTML = "<font class = math>r</font> must be less than <font class = math>n</font>. Try again.";
else document.getElementById("permutationAnswer").innerHTML =  "<font class = math>P</font>(" +  n.toString() + ", " + r.toString() + ") = " + value;
}


function processFactorial() {
var n = document.factorialForm.input.value;
	try
		{
 		var value = factorial(parseInt(n),1);
		}
	catch (error)
		{
 		 document.getElementById("factorialAnswer").innerHTML = "You must enter a positive integer first. Try again.";
		}

if ((n == '')|| (parseInt(n) < 0) || (Math.floor(n) != n)) document.getElementById("factorialAnswer").innerHTML = "You must enter a positive integer. Try again.";
else document.getElementById("factorialAnswer").innerHTML =  n.toString() + "! = " + value;
}

function processCombination() {

var n = document.combinationForm.inputN.value;
var r = document.combinationForm.inputR.value;

	try
		{
 		var value = nCr(parseInt(n), parseInt(r));
		}
	catch (error)
		{
 		 document.getElementById("combinationAnswer").innerHTML = "You must enter two positive integers first. Try again.";
		}


if ((n == '')|| (parseInt(n) < 0) || (Math.floor(n) != n)) document.getElementById("combinationAnswer").innerHTML = "<font class = math>n</font> must be a positive integer. Try again.";
else if ((r == '')|| (parseInt(r) < 0) || (Math.floor(r) != r)) document.getElementById("combinationAnswer").innerHTML = "<font class = math>r</font> must be a positive integer. Try again.";
else if (parseInt(n) < parseInt(r)) document.getElementById("combinationAnswer").innerHTML = "<font class = math>r</font> must be less than <font class = math>n</font>. Try again.";
else document.getElementById("combinationAnswer").innerHTML =  "<font class = math>C</font>(" +  n.toString() + ", " + r.toString() + ") = " + value;
}



function nCr(N, R){


  R=parseInt(R);
  N=parseInt(N);



 

  if(R==N)
  {
	temp=1;
	
	return temp.toString();
  }


  if((R)>(N/2))
  {

	R=N-R;

  }

  var denom=N-R;

  

  var answer2=factorial(N, denom);

  var tmp=factorial(R, 0);

  answer2=answer2/tmp;

  return answer2.toString();  





}

function nPr(N, R){

  R=parseInt(R);
  N=parseInt(N);






  var denom=N-R;

  

  var answer2=factorial(N, denom);
  

  return(answer2.toString());



}


function factorial(intput, limit){





  intput = Math.round(intput);

  var answer = 1;

  

  for(counter = intput; counter>limit; counter=counter-1)
	{
	  answer = answer*counter;
	}



  return answer.toString();


}