import java.util.*;
class Main
{
public static void main
(String[] args
) {
Scanner in
= new Scanner
(System.
in); double a, y;
a = in.nextDouble();
if (a < -1){
y = 1/(a*a);
}
else{
if (a >= -1 && a <= 2) y = a*a;
else y = 4;
}
System.
out.
printf("%.8f\n", y
); }
}
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