This function is used to extract, from a chain where are distributed telephone numbers, a number following its position in the chain.
Chain example:
"Pitaluga has several telephone numbers: 06 66 99 55 78 & 294 54 20 44 & 099 925 301 & 06 300 200 11 & 095 233 144 & 600 25 52 30"
A phone number...