Time Limit: 1000 ms
Memory Limit: 65535 ms
After many years, robots have become very intellective and popular. Dreaming3000 Corporation is a big company that produces service robots. In order to guarantee the safety of production, each robot has an unique number (each number is selected from 1 to N and will be recorded when the robot is produced).
But one day we found that N+1 robots have been produced in the range of 1 to N , that’s to say one number has been used for 2 times. Now the president of Dreaming3000 Corporation hopes to find the reused number as soon as possible.
N represents the maximum number. The next line has N +1 numbers. (All numbers are between 1 to N, and only two of them are the same.) (1 <= N <= 10 ^ 6)
Output the reused number.