for davood mirzaii

e_cal.cpp

#include<iostream>
using namespace std ;

int fact(int x){
	if(x == 0) return 1 ;
	return x * fact(x-1);
}

int main(){
	int n ;
	float e = 0 ;
	cin >> n ;
	for(int i = 0 ; i <= n ; i++){
		e += 1.0 / (float)fact(i) ;
	}
	cout << e ;
}