I'm trying to write a script that takes two files and a number as its parameters and copies that number of lines from one file to the other. Here's what I have: 

```
#!/bin/bash

file1=$1
file2=$2
lines=$3

sed -n '1,\'$lines\'p' $file1 > $file2

```

Obviously the problem is the formatting of the `$lines` parameter. What's the right way to do this? Thanks!