Forgotten Episode

给定一个长度为N-1的数列,求数列中1到N哪个数没有出现 #### 【输入】 第一行为一个整数N(1<=N<=100000) 第二行为N-1个整数 #### 【输出】 数列中没有出现的数

Polycarpus adores TV series. Right now he is ready to finish watching a season of a popular sitcom "Graph Theory". In total, the season has $ n $ episodes, numbered with integers from $ 1 $ to $ n $ . Polycarpus watches episodes not one by one but in a random order. He has already watched all the episodes except for one. Which episode has Polycaprus forgotten to watch?

The first line of the input contains integer $ n $ $ (2<=n<=100000) $ — the number of episodes in a season. Assume that the episodes are numbered by integers from $ 1 $ to $ n $ . The second line contains $ n-1 $ integer $ a_{1},a_{2},...,a_{n} $ $ (1<=a_{i}<=n) $ — the numbers of episodes that Polycarpus has watched. All values of $ a_{i} $ are distinct.

Print the number of the episode that Polycarpus hasn't watched.

10
3 8 10 1 7 9 6 5 2

4