#### Topic: The total of nonblank elements of recursions

It is used XSLT 1.0. Is XML:

```
<root>
<SUM_1> 10 <SUM_1>
<SUM_2> 7 <SUM_2>
<SUM_5> <SUM_5>
<SUM_6> 3 <SUM_6>
<SUM_11> 1 <SUM_11>
<SUM_15> 12 <SUM_15>
<root>
```

In total elements SUM _ <N> can be 15. There can be everything, there can be some, some can be empty.

It is necessary to count the total of all elements. I know that the task c the help of a recursion dares, but the further advancements on this subject of result did not give. Help, please.