I am working with the following (suboptimal) XML:

```
<a>
  <b>
    <c>X:1 Y:0</c>
    <c>X:1 Y:0</c>
    <c>X:2 Y:0</c>
  </b>
  <b>
    <c>X:1 Y:0</c>
    <c>X:2 Y:0</c>
  </b>
</a>

```

I am trying to use XPath to count the number of `<c>` nodes whose contents contain `X:1`:

```
count(contains(/a/b/c, 'X:1'))

```

However, this returns an error rather than returning the expected count of `3`.

What am I doing wrong?