using System;

public class Program

{

    public static void Main()

    {

        double e, dh, Re, f;

        e = 0.0005;

        dh = 0.75;

        Re = 52500;

        f = DarcyFrictionFactor(e, dh, Re);

    }

    public static double DarcyFrictionFactor(double AbsoluteRoughness, double HydraulicDiameter, double ReynoldsNumber)

    {

        double AR = AbsoluteRoughness;

        double HD1 = HydraulicDiameter;

        double RN = ReynoldsNumber;

        double tol = 0.000001;

        double x, Xold, DeltaX, f;

        f = 0.001;

        Xold = f - 0.00001;

        x = f;

        for(int i = 0; i<100; i++)

        {

            DeltaX = (x - Xold) / (1 - (Math.Sqrt(Xold) * (1.14 - 2 * Math.Log(AR / HD1 + 9.35 / (RN * Math.Sqrt(Xold))) / Math.Log(10)) - 1) / (Math.Sqrt(x) * (1.14 - 2 * Math.Log(AR / HD1 + 9.35 / (RN * Math.Sqrt(x))) / Math.Log(10)) - 1));

            Xold = x;

            x = x - DeltaX;

            if(Math.Abs(DeltaX) < tol){break;}

        }

        f = Math.Round(x*1000000)/1000000;

        return f;

    }

    public static double DarcyWeisbach(double DarcyFactor, double Length, double Velocity, double Density, double HydraulicDiameter)

    {

        double Darcy=0;

        return Darcy;

    }

}