package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
)

func solve(in io.Reader, out, err io.Writer) {
	var value, weight, volume int
	fmt.Fscan(in, &value, &weight, &volume)

	coins := value / 5
	weight = weight * coins
	fmt.Fprintf(out, "%.12f", float64(weight)/float64(volume))
}

func main() {
	br := bufio.NewReaderSize(os.Stdin, int(1e3))
	solve(br, os.Stdout, os.Stderr)
}