Java :

import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
	     Scanner input = new Scanner(System.in);
	     int a = input.nextInt();
	     int i = 1;
	     double sum = 0;
	     while(i<=a){
         sum = sum+1/((Math.pow(i, 0.5))+(Math.pow(i+1, 0.5)));
	    	 i=i+1;
	     }
		System.out.println(sum);
	}

}