import java.util.Scanner;

public class HarmonicSumCalculator {

  
    public static String calculateHarmonicSum(int n) {
        if (n < 1) {
            return "-1";
        }
        
        double harmonicSum = 0.0;
        for (int i = 1; i <= n; i++) {
            harmonicSum += 1.0 / i;
        }
        return String.format("%.2f", harmonicSum);
    }
    // -----------------------------------------------------------------

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        if (!scanner.hasNextInt()) {
            System.out.println("Invalid input");
            scanner.close();
            return;
        }
        
        int n = scanner.nextInt();
        
        if (n < -50 || n > 50) {
            System.out.println("Invalid input");
            scanner.close();
            return;
        }

        scanner.close();

    
        
        System.out.println(result);
    }
}