{
task:sum
lang:pascal
}
program sum;
var a:array [1..19] of integer;
    n,m,i:byte;
begin
read(n);
for i:=1 to n do
 read(a[i]);
m:=0;
for i:=n downto 1 do
 m:=m+i;
m:=m+1;
writeln(m);
end.