It is the last month of 2019 which means only few months left for new incoming juniors . keeping this in mind our seniors written a software which automatically assigns a random rollno(roll no are strictly +ve and unique) But there is a bug in this software :(

Bug Report :
For given n it only allocates n-1 rollno and misses a single number
Ex:
10
1 3 5 2 4 7 8 10 9
it misses the roll no 6

Since seniors has a hard time with academics hence they left the work in middle. You need to complete this software. You need to write a program to find that missing number from given number

input:

first line consists of a integer n

next line contains n-1 positive integers ranging from 1 to n.

constraints:
1 <= n <= 100