Chef and Picnic

The chef is planning for a picnic with the chapter leaders and booked $N$ vehicles for the picnic. All $N$ vehicles are parked in a straight line outside the Chef's restaurant. Chef asks all chapter leaders to go and sit on $N$ vehicles and they sat randomly such that for each valid $i$, the vehicle at $i$th position consists of $P_i$ Passengers (Chapter leaders). The chef noticed that stil