import java.util.Arrays;
import java.util.Scanner;
public class Polynomial_Summation {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while (scanner.hasNext()) {
//几个数据
String m = scanner.nextLine();
//测试的实例
String n = scanner.nextLine();
String[] strs = n.split(" ");
int[] instance = new int[100];
for (int i = 0; i < strs.length; i++) {
instance[i] = Integer.parseInt(strs[i]);
double sum = 0.0;
for (int j = 1; j <= instance[i]; j++) {
if (j%2 == 0) {
sum = sum - (double)1/j;
}else {
sum = sum + (double)1/j;
}
}
System.out.println(String.format("%.2f", sum));
}
}
}
}
注意:两个整数相除自动舍去小数。