#include <iostream>
using namespace std;
double  jie(int a){
    double m=1;
    for (int i=2;i<=a;i++){
        m=m*i;
    }
    return m;
}
int main()
{
    int n;
    double e=1;
    cin>>n;
    for(int j=1;j<=n;j++){
        e+=1.0/jie(j);
    }
    printf("%.10f",e);
    return 0;
}

c++

def fac(n):
    if n == 0:
        return 1
    else:
        return fac(n-1)*n

n = int(input())
ans = 1
for i in range(1,n+1):
    ans+=1/fac(i)
print("%.10f"%ans)

#include

using namespace std;

int main() {double n,a=1,b=1; cin>>n; for (int i=1;i<=n;i++){ a=a/i; b=b+a; } printf("%.10f",b); return 0; }