/********************************************************************
@file     Main.cpp
@date     2017-05-12
@author   Zoro_Tiger
@brief    问题 1018: C语言程序设计教程（第三版）课后习题6.8
          http://www.dotcpp.com/oj/problem1018.html
********************************************************************/
#include <cstdio>

#define TEST
#undef  TEST

int main(int argc, const char* argv[])
{

#ifdef TEST
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif

    int number_n = 0;
    while (scanf("%d", &number_n) != EOF)
    {
        double a = 1, b = 2, sum = 0;
        for (int i = 0; i < number_n; ++i)
        {
            sum += b / a;
            a = a + b; //!a值本身的值被舍弃

            //!交换
            a = a + b;
            b = a - b;
            a = a - b;
        }
        printf("%.2lf\n", sum);
    }

    return 0;
}