var i,n,sum:integer;
Begin
read(n);
i:=1;
sum := 0;
while i<=n do
begin
sum := sum + i;
i := i + 2;
end;
write(sum);
end.
var i,n,sum:integer;
Begin
read(n);
i:=1;
sum := 0;
while i<=n do
begin
sum := sum + i;
i := i + 2;
end;
write(sum);
end.