Consider the following program :
int f(int *p, int n)
{
      if(n <= 1) return 0;
    else return max (f (p+1, n–1), p[0]–p[1]);
}
int main()
{
int a[] = {3, 5, 2, 6, 4};
printf(“%d”, f(a, 5));
}
Note : max(x, y) returns the maximum of x and y. The value printed by this program is ________ .