#include <stdlib.h>
#include <time.h>
#include "iostream"
#include <math.h>
using namespace std;
double p;
//n is the length of a car
double n;
double e = 0.0000001;
//double e = 0;
int interval(double l);
int interval(double l, double a){
	a = a - floor(a);
	//Length < 1.0
	if(l<n-e) return 0;

	double t = ((double) rand())/((double) RAND_MAX);

	if(t>p){
		//bad driver
		t = ((double) rand())/((double) RAND_MAX)*(l-n);
		return interval(t,a) + interval(l-t-n,a-t) + 1;
	}else{
		//good driver
		if(l-a<n){
			//the car has to park behind another car
			//Clearly the interval l can be treated as having no lines
			//break into 2 smaller pieces
			return interval(l-n)+1;
		}else{
			t = floor(((double) rand())/((double) RAND_MAX)*floor(l-n-a));
			return interval(t+a,a) + interval(l-a-t-n,1-n) + 1;
		}
	}
}
int interval(double l){
	if(l<n-e){
		return 0;
	}
	double t = ((double) rand())/((double) RAND_MAX);
	if(t>p){
		t = ((double) rand())/((double) RAND_MAX)*(l-n);
		return interval(t) + interval(l-t-n) + 1;
	}else{
		return interval(l-n)+1;
	}
}
int main(int argc, char* argv[]) {
	srand(time(NULL));
	double l = atof(argv[1]);
	p = atof(argv[2]);
	//int z = atoi(argv[3]);
	double z = atof(argv[3]);
	n = (1.0 / (double) z);
	int itr = atoi(argv[4]);
	long t=0;
	l=l/z;
	for(int i=0;i<itr;i++){
		t+= interval(l,0);
	}
	cout << ((double) t )/ ((double) itr )/ l * n << endl;
	return 0;
}