// Arup Guha
// 8/4/2021
// Solution to 2021 UCF Qualifying Contest Problem: How Much Coffee is Left?

import java.util.*;

public class coffee {

	public static void main(String[] args) {
	
		Scanner stdin = new Scanner(System.in);
	
		// Get the input.
		double smallR = stdin.nextInt();
		double bigR = stdin.nextInt();
		double height = stdin.nextInt();
		double numMin = stdin.nextInt();
		double newDepth = stdin.nextInt();
		
		// Now figure out the radius of the top of the surface of coffee after drinking some.
		double newR = smallR + (bigR-smallR)*newDepth/height;
		
		// Since the figures grow in cube to the proportion of radii, we have the following...these aren't actual volumes,
		// but the actual volume times a constant.
		double drank = bigR*bigR*bigR - newR*newR*newR;
		double left = newR*newR*newR - smallR*smallR*smallR;

		// So all we do here is a ratio of what's left to what we drank multiplied by the number of minutes it took
		// to drink the first part.
		System.out.printf("%.9f\n",left/drank*numMin);
	}
}