package main
 
import "fmt"
import "math"
 
type geometry interface {
    area() float64
    perim() float64
}  
 
type rect struct {
    width, height float64
}
 
func (r rect) area() float64 {
    return r.width * r.height
}
 
func (r rect) perim() float64 {
    return 2*r.width + 2*r.height
}