package main

import (
    "fmt"
    "math"
)

type Vertex struct {
    X, Y float64
}

func Abs(v Vertex) float64 {
    return math.Sqrt(v.X * v.X + v.Y * v.Y)
}

func main() {
    v := Vertex{3 ,4}
    fmt.Println(Abs(v))
}