var summa: real;
N, i:integer;
begin
read(N);
summa:= 0;
for i:=N downto -4 do
summa := summa + i
end.
var summa: real;
N, i:integer;
begin
read(N);
summa:= 0;
for i:=N downto -4 do
summa := summa + i
end.