#include <iostream>
#include <fstream>
using namespace std;
double f(double x) {
    double sum = 0;
    double cur = 1;
    int n = 0;

    while (cur > 1e-10 or cur < -1e-10) {
        sum += cur;
        ++n;
        cur *= -x * x / (2 * n * (2 * n - 1));
    }

    return sum;
}
// средние прямоугольники
double middle(double a, double b, double Eps) {
    double h = (b - a);
    double integral = f((b-a)/2);
    double prev_integral = 0;

    while (fabs(integral - prev_integral) >= Eps) {
        prev_integral = integral;
        integral = 0;
        h = h / 2;
        for (double x = a + h / 2; x < b; x += h) {
            integral += f(x);
        }
        integral *= h;
    }
    return integral;
}
// правые прямоугольники
double right(double a, double b, double Eps) {
    double h = (b - a);
    double integral = f((b - a) / 2);
    double prev_integral = 0;

    while (fabs(integral - prev_integral) >= Eps) {
        prev_integral = integral;
        h = h / 2;
        for (double x = a + h; x <= b; x += h) {
            integral += f(x);
        }
        integral *= h;
    }

    return integral;
}
// трапеции
double trapezia(double a, double b, double Eps) {
    double h = (b - a);
    double integral = (f(a)+f(b))/2;
    double prev_integral = 0;

    while (fabs(integral * h - prev_integral * 2* h) >= Eps) {
        prev_integral = integral;
        h = h / 2;
        for (double x = a + h; x <= b; x += 2*h) {
            integral += f(x);
        }
    }

    return integral * h;
}
int main()
{
    ifstream input("input.txt");
    double a = 0;
    double b = 0;
    double Eps = 0;
    int method = 0;
    input >> a >> b >> Eps >> method;
    switch (method) {
    case(1):
        cout << right(a, b, Eps);
        break;
    case(2):
        cout << middle(a, b, Eps);
        break;
    case(3):
        cout << trapezia(a, b, Eps);
        break;
    }
}