Program HOC24;
var i,n: integer;
S: longint;
begin
write('Nhap N: '); readln(n);
i:=1; s:=0;
while i<=n do
begin
s:=s+i;
i:=i+2;
end;
write('S=',S);
readln
end.
program tinh_tong_S;
var
n, i, S: integer;
begin
write('Nhap n: ');
readln(n);
S := 0;
i := 1;
while i <= n do
begin
S := S + i;
i := i + 2;
end;
writeln('Tong S la: ', S);
readln;
end.