Consider a disk queue with requests for I/O to blocks on cylinders 135, 27, 230, 181, 65, 378, 42, 140, 420. The elevator scheduling algorithm is used. The head is initially at cylinder number 99. The cylinders are numbered from 0 to 499. The total head movement (number of cylinders) incurred while servicing these requests is ______.(assume that elevator algorithm moves towards 0 when it start its execution)