write a shell script programming to find the maximum of three number

i wrote a program but it doesnt work please help?

!/bin/bash echo "enter the first number" read first echo "enter the second number" read second echo "enter the third number" read third if [Sfirst -gt $sec]; then if [ Sfirst -gt $third ] then echo -e "Sfirst is the maximum number" else echo -e "$third is the maxtmum number" fi else if [ssecond -gt $third]; then echo -e "$second is the maximum number" else echo -e "$third is the maxtmum number" fi fi