uses crt;
var i,n,s:integer;
begin
read(n);
s := 0;
for i := 1 to n do begin
s := s + i;
end;
writeln(s);
end.
uses crt;
var i,n,s:integer;
begin
read(n);
s := 0;
for i := 1 to n do begin
s := s + i;
end;
writeln(s);
end.