given input a sequence to determine if it is increasing or decreasing

hi given a sequence I have to check if it is increasing or decreasing, I did it but it doesn't work for me how can I solve it?

#!/bin/bash
tot=0
numeri=0
media=0
cresc=0
decresc=0

for number in $@ 
do
    tot=$((tot+number))
    numeri=$((numeri+1))
done
 
echo TOTALE = $tot
media=$((tot/numeri))
echo MEDIA = $media


if [ $cresc -eq 0 ]
then echo SEQ. CRESCENTE
else echo SEQ. DECRESCENTE
fi

output:

user insert: 1 2 4
system response: the sequence is increasing

user insert: 4 3 2

system response: the sequence is decreasing

What about this simple and readable one?

#!/bin/bash

crescente=0
decrescente=${#@}
dec=$decrescente

for number; do
    if [[ ! $number =~ ^-?[0-9]+$ ]]; then
        echo "C'È ALMENO QUALCOSA CHE NON È UN NUMERO" >&2
        exit 1
    fi

    if [[ $last ]]; then
        if ((last < number)); then
            ((crescente++))
        elif ((last > number)); then
            ((decrescente++))
        fi
    fi
    last=$number
done

if ((crescente && decrescente == dec)); then
    echo "SEQ. CRESCENTE"
elif ((descrecente < dec && crescente == 0)); then
    echo "SEQ. DECRESCENTE"
else
    echo "NON ORDINATO" >&2
    exit 1
fi

((...)) is an arithmetic command, which returns an exit status of 0 if the expression is nonzero, or 1 if the expression is zero. Also used as a synonym for "let", if side effects (assignments) are needed. See <http://mywiki.wooledge.org/ArithmeticExpression>.

Example output

$ ./seq.sh 1 2 x
CÈ ALMENO QUALCOSA CHE NON È UN NUMERO
$ ./seq.sh 1 2 3
SEQ. CRESCENTE
$ ./seq.sh 3 2 1
SEQ. DECRESCENTE
$ ./seq.sh 3 2 1 0
SEQ. DECRESCENTE
$ ./seq.sh 3 2 1 0 -1
SEQ. DECRESCENTE
$ ./seq.sh -42 42 $((2**42))
SEQ. CRESCENTE
$ ./seq.sh 3 5 2
NON ORDINATO