#include <iostream>
using namespace std;

double e (int x, int n)
{
    static double p=1, f=1;
    double r=0;
    if (n==0)
        return 1;
    else
        r = e(x,n-1);
        p=p*x;
        f=f*n;
        return r+(p/f);
}

int main() {
    double sum= e(1,10);
    cout << sum;
    return 0;
}