HOJ ( acm.hdu.edu.cn ) 2011

#include <iostream>
using namespace std;

double f(int n) {
  double ans=0;
  for ( int i=1; i<=n; i+=2 )
      ans+=1.0/i;
  for ( int i=2; i<=n; i+=2 )
      ans-=1.0/i;
  return ans;
}

int main()
{
  int n,i;
  for (cin>>n; n; --n) {
      cin>>i;
      cout.precision(2);
      cout<<fixed<<f(i)<<endl;
  }
  return 0;
}