What should come in place of ? in the above algorithm?

An algorithm to delete the node/key k from a tree T is given below:
delete(T, k)
{
if(left[k] == null && right[k] == null)
{
K = null;
}
else if(left[k] != null && right[k] == null)
{
if(k == left[parent[k]]) left[parent[k]] == left[k];
else right[parent[k]] = left[k];
 }
else if(left[k] == null && right[k] != null)
{
if(k == left[parent[k]]) left[parent[k]] == right[k];
else right[parent[k]] = right[k];
 }
else Y = ?;
X = y;
Right[x] = left[y];
 }
}