using System;
using System.Threading;
using static System.Console;
class main{

public class data { public int a,b; public double sum;}

public static void harm(object obj){
	data d = (data)obj;
	WriteLine($"harm: summing from {(float)d.a} to {(float)d.b} ...");
	d.sum=0; for(int i=d.a;i<d.b;i++)d.sum+=1.0/i;
	WriteLine($"harm: summing from {(float)d.a} to {(float)d.b} gives {d.sum}");
	}

public static void Main(string[] args){
	int N = (int)1e8;
	if(args.Length>0) N = (int)double.Parse(args[0]);
	WriteLine($"---------\ntwo threads: harm sum: N={(float)N}");
	data x = new data();
	x.a=1; x.b=N/2;
	data y = new data();
	y.a=N/2; y.b=N+1;
	Thread t1 = new Thread(harm);
	Thread t2 = new Thread(harm);
	t1.Start(x);
	t2.Start(y);
	t1.Join();
	t2.Join();
	WriteLine($"two threads: harm sum from {1} to {(float)N} = {x.sum+y.sum}");

}

}