#include<iostream>
#include<cmath>

using namespace std;

double FunctionX(double t, double x, double y) {
    return -1 / t*x + y;
}

double FunctionY(double t, double x, double y) {
    return -(2 * x) / (t*t) + y / t;
}

int main()
{
    int l, n = 2000;
    double t0 = 1, t3 = 3;
    double K1_1[2], K1_2[2], K2_1[2], K2_2[2];
    double x = 1, y = 1, h = fabs((t3 - t0) / n), temporary, T0 = t0;


    for (int w = 1; w <= n; w++)
    {

        for (int i = 0; i < 2; i++)
        {
            switch (i) {
            case 0: temporary = h * FunctionX(T0, x, y);
                break;
            case 1: temporary = h *FunctionY(T0, x, y);
                break;
            }
            K1_1[i] = temporary;
        }

        for (int i = 0; i < 2; i++)
        {
            switch (i) {
            case 0: temporary = h*FunctionX(T0 + 0.5*h, x + 0.5*K1_1[0], y + 0.5*K1_1[1]);
                break;
            case 1: temporary = h*FunctionY(T0 + 0.5*h, x + 0.5*K1_1[0], y + 0.5*K1_1[1]);
                break;
            }
            K1_2[i] = temporary;
        }

        for (int i = 0; i < 2; i++)
        {
            switch (i) {
            case 0: temporary = h*FunctionX(T0 + 0.5*h, x + 0.5*K1_2[0], y + 0.5*K1_2[1]);
                break;
            case 1: temporary = h*FunctionY(T0 + 0.5*h, x + 0.5*K1_2[0], y + 0.5*K1_2[1]);
                break;
            }
            K2_1[i] = temporary;
        }

        for (int i = 0; i < 2; i++)
        {
            switch (i) {
            case 0: temporary = h*FunctionX(T0 + h, x + K2_1[0], y + K2_1[1]);
                break;
            case 1: temporary = h*FunctionY(T0 + h, x + K2_1[0], y + K2_1[1]);
                break;
            }
            K2_2[i] = temporary;
        }

        x = x + (K1_1[0] + 2 * K1_2[0] + 2 * K2_1[0] + K2_2[0]) / 6;
        y = y + (K1_1[1] + 2 * K1_2[1] + 2 * K2_1[1] + K2_2[1]) / 6;
        T0 = t0 + w*h;
        l = w;

    }


    cout << "Ilosc iteracji : " << l << endl;
    cout << " x(3) = " << x << endl;
    cout << " y(3) = " << y << endl;



    system("pause");
    return 0;
}