function frac(){
    readonly mul=1000000
    readonly mullen=${#mul}
    local a=$1
    local b=$2
    local tmp=`printf "%0${mullen}d" $((a*mul/b))`
    local tmplen=${#tmp}
    local ilen=$((tmplen-(mullen-1)))
    local flen=$((mullen-1))
    echo ${tmp:0:$ilen}"."${tmp: -$flen}
    }
read l
frac $((l*l*l)) 27