#include<bits/stdc++.h> using namespace std; int main() { cout<<2.7182818011<<endl; return 0; }

#include<bits/stdc++.h> using namespace std; int main(){ int n,e = 1,fm = 1; cin >> n; for (int i = 1 ; i <= n ; i++) { fm = fm * i; e = e + 1 / fm; } cout << fixed << setprecision(10) << e << endl;

return 0;

}

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