How To Make Function Cover All Possible Radio Buttons?

I Have to sets of Radio buttons like so:

<input type="radio" name=p1 value=1>
<input type="radio" name=p1 value=2>
<input type="radio" name=p1 value=3>
<br>
<input type="radio" name=p2 value=1>
<input type="radio" name=p2 value=2>
<input type="radio" name=p2 value=3>

then a text area and a button:
<input size=7 name=total>
<input type="button" onclick=c()>

the function checks for the radio buttons then outputs its value in text
area.

<script type="text/javascript">
function c()
{if (p1[a].checked&&p2[b].checked)
total.value=parseFloat(p1[a].value)+parseFloat(p2[b].value)
}</script>

my question is what is the possibility of giving values to a and b such as
all radio buttons can be covered, is there a way to do this without having
to output all cases with else if structure.