Probability

There are five students S1,S2,S3,S4 and S5 in a music class and for them there are five seats R1,R2,R3,R4 and R5 arranged in a row, where initially the seat Ri is allotted to the student Si=1,2,3,4,5.But, on the examination day, the five students are randomly allotted the five seats.

The probability that, on the examination day, the student S1 gets the previously allotted seat R1, and NONE of the remaining students gets the seat previously allotted to him/her is