Do you know how hard it is to pull the trigger?
The famous dictator Lee Xi Seung has an army of at his disposal. He numbered them from to . The lower the number a person has, the higher his commanding abilities. Then he repressed of them. Now the dictator is going to conduct a small victorious war with a neighboring state. Therefore, he urgently needs to choose the most talented military who is alive.
The first line contains the number of repressed . The second line contains their numbers in Lee Xi Seung's list — all numbers less than .
Print one number — the number of the most talented alive military.