import java.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;

class InfiniteSum {
	public static void main (String[] args) throws java.lang.Exception {
		//Scanner read = new Scanner(System.in);
		double E = 1e-1;
		double x = -1;
		double sum = 0.0;
		for(int i = 2; Math.abs(x) > E ; i++){
			sum += x;
			x *= (-1./i);
		}
		System.out.print("Сумма = "+sum);
	}
}