package main

import (
	"fmt"
)
type ErrNegativeSqrt float64

func (e ErrNegativeSqrt) Error() string {
	return fmt.Sprintf("cannot Sqrt negative number:%v\n",(e))
	
}
func Sqrt(x float64) (float64, error) {
	if x < 0 {
		return 0,ErrNegativeSqrt(x)
	}else{
		return 0, nil
	}
}

func main() {
	fmt.Println(Sqrt(2))
	fmt.Println(Sqrt(-2))
}