A student was given the expression $A-(B-(C-(D-E)))$ to evaluate. The student, ignoring the parentheses, computed the value as $A-B-C-D-E$. By coincidence, this result was correct. If the numbers substituted for $A,B,C,$ and $D$ were $12,11,10,$ and $9$ respectively, what number did the student substitute for $E$?