A student was asked to evaluate the expression $m-(n-(p-(q+r)))$. The student, ignoring the parentheses, computed the value as $m-n-p-q+r$. By coincidence, this result was correct. If the numbers substituted for $m,n,p,$ and $q$ were $10,8,6,$ and $4$ respectively, what number did the student substitute for $r$?