#include <iostream>
using namespace std;
int main() {
int n;
float factn=1,m,sum;
cout<<"enter nn";
cin>>n;
if(n<10&&n>=0){
do{
        factn=factn*n;
        m=1/factn;
        sum=sum+m;
        n--;
    }while(n>=1);
        cout<<sum;
}
else{
    cout<<"error!n";
}
return 0;

}