fun getK1(x: Double, t: Double): Double = func(x, t)

    fun getK2(x: Double, t: Double, h: Double): Double = func(x + h / 2 * getK1(x, t), t + h / 2)

    fun getK3(x: Double, t: Double, h: Double): Double =
        func(x + h / 4 * getK1(x, t) + h / 4 * getK2(x, t, h), t + h / 2)

    fun getK4(x: Double, t: Double, h: Double): Double = func(x - h * getK2(x, t, h) + 2 * h * getK3(x, t, h), t + h)

    fun getK5(x: Double, t: Double, h: Double): Double =
        func(x + h / 27 * (7 * getK1(x, t) + 10 * getK2(x, t, h) + getK4(x, t, h)), t + 2.0 / 3 * h)

    fun getK6(x: Double, t: Double, h: Double): Double =
        func(
            x + h / 625 * (28 * getK1(x, t) - 125 * getK2(x, t, h) + 546 * getK3(x, t, h) + 54 * getK4(
                x,
                t,
                h
            ) - 378 * getK5(x, t, h)),
            t + 1.0 / 5 * h
        )

    fun getDelta(x: Double, t: Double, h: Double) =
        h / 336 * (-42 * getK1(x, t) - 224 * getK3(x, t, h) - 21 * getK4(x, t, h) + 162 * getK5(
            x,
            t,
            h
        ) + 125 * getK6(x, t, h))

    fun compute4(x: Double, t: Double, h: Double) =
        1.0 / 6 * (getK1(x, t) + 4 * getK3(x, t, h) + getK4(x, t, h)) // h**4

    fun compute5(x: Double, t: Double, h: Double) =
        1.0 / 336 * (14 * getK1(x, t) + 35 * getK4(x, t, h) + 162 * getK5(x, t, h) + 125 * (getK6(x, t, h))) // h**5

    fun deltaGraph(x0: Double, t0: Double, T: Double, count: Int): Array<Double> {
        val h = (T - t0) / count;
        var t = t0;
        var x = x0
        var result = ArrayList<Double>()
        while (t < T) {
            t += h
            result.add(getDelta(x, t, h))
            x += h * compute4(x, t, h)
        }

        return result.toArray(Array<Double>(0) { 0.0 })
    }

    fun integrate4(x0: Double, t0: Double, T: Double, count: Int): Array<Double> {
        val h = (T - t0) / count;
        var t = t0;
        var x = x0
        var result = ArrayList<Double>()

        while (t < T) {
            x += h * compute4(x, t, h)
            t += h
            result.add(x)
        }

        return result.toArray(Array<Double>(0) { 0.0 })
    }

    fun integrate5(x0: Double, t0: Double, T: Double, count: Int): Array<Double> {
        val h = (T - t0) / count;
        var t = t0;
        var x = x0;
        var result = ArrayList<Double>()

        while (t < T) {
            x += h * compute5(x, t, h)
            t += h
            result.add(x)
        }
        return result.toArray(Array<Double>(0) { 0.0 })
    }