calculate the frequency for all characters occurring in the text file.

To do this, calculate a list of pairs of frequency and characters of type vector$>$ sorted

by frequency in descending order. Output the list as in the following example for texte$/$sample$1.$txt$.$

e: $41$ : $34$ n: $26$ i: $24$ h: $15$ a: $14$

r: $13$ s: $12$ c: $11$ u: $9$ l: $9$ d: $9$

t: $8$ z: $7$ b: $6$ p: $5$ o: $5,$: $4$

: $4$ w: $3$ v: $3.$: $3$ m: $2$ k: $2$

f: $2$ x: $1$