package main
import(
	. "fmt"
	"os"
	"encoding/hex"
)
var usage = "usage: hexdecode hexstr"

func Error(s interface{}){
	Fprintln(os.Stderr,s)
	os.Exit(1)
}

func main(){
	args := os.Args[1:]
	if len(args) != 1 {
		Error(usage)
	}
	bs,err := hex.DecodeString(args[0])
	if err != nil {
		Error(err)
	}	
	Print(string(bs))
}