Program n1;
var i,n: integer;
sum: real;
function fact(n: integer): real;
var i: integer;
p: real;
begin
p:=1;
for i := 2 to n do p:= p*i;
fact:=p;
end;
begin
write('n=');
readln(n);
sum:=0;
for i:=1 to n do sum:=sum+fact(i);
writeln('sum=',sum);
end.