program program4;
const u: array[0..2] of integer = (1,-3,2);
v: array[0..1] of integer = (-2,3);
var i, n, sum:integer;
function g(n:integer): integer;
var i, sum:integer;
begin
sum:=0;
for i:=1 to n do inc(sum,u[i mod 3]*i);
g:=sum;
end;
begin
sum:=0;
read(n);
for i:= 1 to n do inc(sum,v[i mod 2]*g(i));
writeln(sum);
end.
输入：１０３
输出：＿＿＿＿＿＿＿＿＿＿．
