Program chisla;
var y,x,a,b,c,d,e: real;
begin
ReadLn(x);
a:=x-3;
b:=x-5;
c:=a*b;
d:=x-2;
e:=sqrt(d);
y:=e/c;
WriteLn (y);
end.
Program chisla;
var y,x,a,b,c,d,e: real;
begin
ReadLn(x);
a:=x-3;
b:=x-5;
c:=a*b;
d:=x-2;
e:=sqrt(d);
y:=e/c;
WriteLn (y);
end.