maxim9(0.5)

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

using namespace std;

double f(double x) {
    return x * atan(x);
}

int main() {
    int n = 1;
    double a = 0, b = 3, eps = 0.001, s_last = 0, s_cur = 0, h;
    for (; n < 4 || fabs(s_cur - s_last) > eps; n <<= 1) {
        h = (b - a) / n;
        s_last = s_cur;
        s_cur = 0;
        for (int i = 1; i <= n; ++ i) {
            s_cur += h * f(a + (i - 0.5) * h);
        }
    }
    cout << s_cur << endl;
    return 0;
}