#include <math.h>
#include <stdio.h>

// Function prototypes
double expe(double x);
double my_pow(double x, double l);
double get_sing(double x, int l);

int main(void) {
  // Initial variables
  double x;
  scanf("%lf", &x);

  printf("%.4lf\n", expe(x));
  return 0;
}

double expe(double x) {
  double ans = 0;
  double addup;
  for (int i = 0;; i++) {
    addup = (get_sing(x, i));
    if (fabs(addup) < 1e-8) {
      break;
    }
    ans += addup;
  }
  return ans;
}

double my_pow(double x, double l) {
  double ans = 1;
  for (long long i = 0; i < l; i++) {
    ans *= x;
  }
  return ans;
}

double get_sing(double x, int l) {
  if (l <= 0) {
    return 1;
  } else {
    double ans = my_pow(x, l);
    for (int i = l; i > 1; i--) {
      ans /= i;
    }
    return ans;
  }
}