#include <iostream>

double f(double x) {
	// implement the function here
	return double(1)/(1+x);
}

double simpson(double a, double b, int n, double _f(double)) {
	int m = n/2;
	double x = a, sigma1 = 0, sigma2 = 0;
	double h = (b-a)/(2*m);
	for (int i = 1; i < 2*m; i++) {
		x = a + i*h;
		if (i%2 != 0)
			sigma1 += _f(x);
		else
			sigma2 += _f(x);
	}
	return (h/3)*(_f(a) + _f(b) + 4*sigma1 + 2*sigma2);
}

int main() {
	std::cout << simpson(0, 1, 10, f);
	return 0;
}