1)
var
n, i, s:integer;
begin
s := 0;
readln(n);
if n mod 2 = 0 then
n := n div 2 -1
else
n := n div 2;
for i := 0 to n do
begin
s := s + (1+2*i)
end;
write(s)
end.
2)
var
a, s: integer;
begin
s := 0;
read(a);
while (a >= 0) do
begin
s := s + a;
read(a)
end;
writeln;
write(s)
end.
var
a, s: integer;
begin
s := 0;
a := 0;
repeat
s := s + a;
read(a)
until a < 0;
writeln;
write(s)
end.