#!/bin/bash

INPUT=$1

PAT="^([0-9]+|([0-9]+).([0-9]+))([GgMmKk])?$"

if [[ ! $INPUT =~ $PAT ]]; then
 echo "error: bad format"
 exit 1
fi

VALUE=$(echo "$INPUT" | sed  "s/[^0-9\.]//g")

case "$INPUT" in
 *G|*g)
   echo $(echo "$VALUE*1024*1024*1024" | bc);;
 *M|*m)
   echo $(echo "$VALUE*1024*1024" | bc);;
 *K|*k)
   echo $(echo "$VALUE*1024" | bc);;
 *)
   PAT_NUM="^[0-9]+$"
   if [[ $INPUT =~ $PAT_NUM ]]; then
      echo "$VALUE"
   else
      echo "NaN"
   fi
  ;;
esac