uses crt;
var n,i:longint;
t:real;
begin
clrscr;
write('n='); readln(n);
if (1<=n) and (n<=10000) then
begin
t:=0;
for i:=1 to n do
t:=t+(1/(sqr(i)));
writeln('T=',t:4:2);
end
else writeln('vui long nhap lai n');
readln;
end.