R: how to shorten a value to just one number inside the value

I have just started to use R.
I have a data frame of chromosome names but I just want to replace the long names with the number of the chromosome.
i.e CHR_HSCHR19LRC_PGF2_CTG3_1 would be "19"
I need to replace the long name with the number just after the characters "HRCHR"
How would I do this?

I tried the method of manually entry the replacement value:
gsub(".*HSCHR19", "19", dataframe)

But this takes far too long for a list of >100 values. I would like to find a way to do this automatically.

>Solution :

You can use

sub('^.*CHR(\\d+).*$', '\\1', Chromosome_name)
#> [1] "7"  "19"