For a positive integer n, we define a function f:f (n)

include lt;iostreamgt;
using namespace std;
int main()

int n = 0, f = 0, t = 0;
cin gt;gt; n;
if (n lt;= 1015 amp;amp; n gt;= 1)
for (int i = 1; i lt;= n; ++i)
    t = -i;
if (i % 2 == 0)
t = абс(t);

cout lt;lt; t lt;lt; " ";
f += t;

else
cout lt;lt; "Error" lt;lt; endl;

cout lt;lt; endl lt;lt; "Res: " lt;lt; f;
return 0;