Freshers Task

Aman a 2nd year student has to set-up a stall at Technofest '15. The stall is set for N days and only one person can work at the stall at a time. There are M first year students who are willing to work at the stall. Each of them is available for a different duration of time, from some day a to day b. If assigned work he/she arrives at the stall on day a and waits for the stall to be vacated(if