#include<bits/stdc++.h> using namespace std; int main() { int n,x,y,z=2,m=1; double sum=0; cin>>n; for(int i=1;i<=n;i++) { sum=sum+1.0*z/m; x=z+m; y=z; z=x; m=y; } printf("%.6f",sum); return 0; }
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