GCJ 2014 - 'Cookie Clicker Alpha' problem solution

CookieClicker.java

package com.bchetty.gcj2014;

import java.text.DecimalFormat;

/**
 * GCJ 2014 - 'Cookie Clicker Alpha' problem soultion

 * @author Babji, Chetty
 */
public class CookieClicker {    
    /**
     * 
     * @param C
     * @param F
     * @param X
     * @param speed
     * @param time
     * @return 
     */
    public String getTimeRequired(double C, double F, double X) {
        DecimalFormat formatter = new DecimalFormat("#.#######");
        double speed = 2.0;
        if(C >= X) {
            return formatter.format((X/speed));
        }        
        double time = 0.0;        
        
        while((X/speed) > (C/speed) + (X/(speed + F))) {
            time += (C/speed);
            speed += F;            
        }
        
        return formatter.format(time + (X/speed));
    }
}