Program tinhtong;
Var n,s,i: integer;
Begin
Write('Hay nhap gia tri cua n'); Readln(n);
s:=0;
For i:=1 to n do s:=1/(2*i+1);
Write('Vay gia tri cua S la: ',s);
End.
uses crt;
var i,n:integer;s:real;
begin
clrscr;
readln(n);
for i:=1 to n do
if i mod 2 <> 0 then
begin
s:=1/i;
i:=i+2;
end;
write(s:2:3);
readln
end.