Program xx304;
var
n:integer;
function sum(k:integer):integer;
var
i,s,t:integer;
begin
s:=0;t:=1;
for i:=1 to k do begin
t:=t*i;
s:=s+t;
end;
sum:=s
end;
begin
n:=5;
writeln(sum(n))
end.
输出：153