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

using namespace std;

double integral(int, int, double, double (*f)(double));
double fun(double);


int main()
{
    int a, b;
    double epsil = 0.001;
    cout << "Please, enter a: ";
    cin >> a;
    cout << "Please, enter b: ";
    cin >> b;
    cout << "Integral = " << integral(a, b, epsil, fun) << endl;
    return 0;
}

double fun(double x)
{
    return x;
}
double integral(int a, int b, double epsil, double (*f)(double))
{
    double s = 0;
    for (double x = a; x < b; x += epsil)
        s += fun(x+epsil);
    return fabs(s)*epsil;
}