#include <iostream>
#include <math.h>

double FX(double x) {
    return x;
}

double FXX(double x) {
    return x * x;
}

double MetodSrednihPryamougolnikov(double a, double b, double countOfParts, double(*func)(double)) {
    double sum = (func(a) + func(b)) / 2.0, step = (b - a) / countOfParts;
    for(double x = a + step; x < b; x += step)
        sum += func(x);
    return sum / countOfParts;
}

double MetodLevihPryamougolnikov(double a, double b, double countOfParts, double(*func)(double)) {
    double sum = 0, step = (b - a) / countOfParts;
    for(double x = a; x < b; x += step)
        sum += func(x);
    return sum / countOfParts;
}

double MetodPravihPryamougolnikov(double a, double b, double countOfParts, double(*func)(double)) {
    double sum = 0, step = (b - a) / countOfParts;
    for(double x = b; x > a; x -= step)
        sum += func(x);
    return sum / countOfParts;
}

double CalcIntegral(double a, double b, double eps, double(*method)(double, double, double, double(*func)(double)), double(*func)(double)) {
    double countOfParts = 4, lastIntegral = method(a, b, countOfParts, func), currentIntegral, diff;
    do {
        currentIntegral = method(a, b, (countOfParts *= 2), func);
        diff = fabs(lastIntegral - currentIntegral);
        lastIntegral = currentIntegral;
    } while(diff > eps);
    return lastIntegral;
}

int main() {
    double a, b, eps;
    std::cout << "Get a:";
    std::cin >> a;
    std::cout << "Get b:";
    std::cin >> b;
    std::cout << "Get eps:";
    std::cin >> eps;

    std::cout << "(f = x,   MetodLevihPryamougolnikov):  " << CalcIntegral(a, b, eps, MetodLevihPryamougolnikov,    FX)  << std::endl;
    std::cout << "(f = x,   MetodSrednihPryamougolnikov):" << CalcIntegral(a, b, eps, MetodSrednihPryamougolnikov,  FX)  << std::endl;
    std::cout << "(f = x,   MetodPravihPryamougolnikov): " << CalcIntegral(a, b, eps, MetodPravihPryamougolnikov,   FX)  << std::endl;
    std::cout << "(f = x*x, MetodLevihPryamouholnikov):  " << CalcIntegral(a, b, eps, MetodLevihPryamougolnikov,    FXX) << std::endl;
    std::cout << "(f = x*x, MetodSrednihPryamougolnikov):" << CalcIntegral(a, b, eps, MetodSrednihPryamougolnikov,  FXX) << std::endl;
    std::cout << "(f = x*x, MetodPravihPryamouholnikov): " << CalcIntegral(a, b, eps, MetodPravihPryamougolnikov,   FXX) << std::endl;
}