package main

import (
    "fmt"
)

func Sqrt(x float64) float64 {
    z := 2.0
    for ; ;  {
        diff := (z*z - x) / (2*z)
        if diff < 0.000000000000000001 {
            break
        }
        z -= diff

    }
    return z
}

func main() {
    f