using System;
class Program {
static void Main() {
Console.Write("N: ");
var n = int.Parse(Console.ReadLine());
var sum = 1.0;
for (var i = 2; i <= n; ++i) {
sum += i % 2 != 0 ? -1.0 / i : 1.0 / i;
}
Console.WriteLine(sum);
Console.ReadKey();
}
}