Write a function definition for a function called in_order that takes three
arguments of type int. The function returns true if the three arguments
are in ascending order; otherwise, it returns false. For example,
in_order(1, 2, 3) and in_order(1, 2, 2) both return true, while
in_order(1, 3, 2) returns false.
bool in_order(int n1, int n2, int n3)
{
return ((n1 <= n2) && (n2 <= n3));
}