function fact {
	local n="$1"
	if [ $n -eq 1 ]; then
	echo $n
	else
		nn=$( fact $((n-1)) )
		echo $(( n*nn ))
	fi
}

function fib {
	local n="$1"
	if[ $n -le 2]; then
	echo $n
	else
		p1=$( fib $((n-1)) )
		p2=$( fib $((n-2)) )
		echo $((p1+p2))
	fi
}

function faciter {
	local p=1
	local cnt=1
	for ((i=1;i<=$1;i++))
	do
	  p=$(($p*$i));
	done
	echo $p
}

function fibiter {
	local f=0
	local s=1
	for ((i=0;i<=$1;i++))
	do
		local tmp=$s
		s=$(($f+$s))
		f=$tmp
	done
	echo $f
}

case "$1" in (fact)
	fact $2
	;;
	(faciter)
	faciter $2
	;;
	(fibiter)
	fibiter $2
	;;
	(fib)
	fib $2
	;;
	(--help)
	echo "Shell script that computes N-th fibonacii number and factoriel of N.
	Usage: fibiter / fib for recursive/ iterative calculation of N-th fibonacii number.
	fact/faciter for calculating factoriel of N!"
	;;
esac