program tinh_tong;
uses crt;
var i,n:integer;
s:real;
begin
clrscr;
write('nhap n:');readln(n);
for i:=1 to n*2-1 do
if i mod 2=1 then s:=s+1/i;
writeln('tong la: ',s);
readln;
end.
program tinh_tong;
uses crt;
var i,n:integer;
s:real;
begin
clrscr;
write('nhap n:');readln(n);
i:=1;
while i<=n*2-1 do
begin
s:=s+1/i;
i:=i+2;
end;
writeln('tong la: ',s);
readln;
end.