Why does this concatenate instead of adding up

[rafiul]

Very very basic question but I've got the following HTML:\[code\]<input type="text" id="nspcc" value="http://stackoverflow.com/questions/12730147/0" onkeyup="doTotal();" /><input type="text" id="barnados" value="http://stackoverflow.com/questions/12730147/0" onkeyup="doTotal();" /><input type="text" id="savethechildren" value="http://stackoverflow.com/questions/12730147/0" onkeyup="doTotal();" /><input type="text" id="childresnsociety" value="http://stackoverflow.com/questions/12730147/0" onkeyup="doTotal();" /><input type="text" id="childreninneed" value="http://stackoverflow.com/questions/12730147/0" onkeyup="doTotal();" /><input type="text" id="total" disabled="disabled" />\[/code\]And the following jQuery:\[code\]function doTotal() { var one,two,three,four,five,total; one = $('#nspcc').val(); two = $('#barnados').val(); three = $('#savethechildren').val(); four = $('#childresnsociety').val(); five = $('#childreninneed').val(); total = one+two+three+four+five; $('#total').val(total);}doTotal();\[/code\]I'm probably doing something daft but why does \[code\]total\[/code\] concatenate instead of adding the values? Do I need to use \[code\]parseInt\[/code\] or something?