Migrated from Lutece 273 The Lost Card

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Description

Having signed a new contract, ArXoR was facing a new task. Given $n$ cards each of which is labeled with an integer bounded in $[-2^{31},2^{31} - 1]$, the task is to make a duplicate copy of these $n$ cards. As usual, this dull work was assigned to TheBeet. After he finished duplicating, he brought the $2 \times n$ cards to ArXoR. But after checking these cards again, they found that one card was lost. It is easy to make a duplication of a card, but not easy to find out which card should be duplicated a again. Could you help these two poor guys , especially, TheBeet.

Input

The input contains a single case. The case begin with a integer $n$ bounded in $[1, 1000000]$.

Then $2 \times n - 1$ lines follows, as mentioned above, each of which indicating the integer on the card in TheBeet and ArXoR's hand.

Output

You should output a single line containing the lost card you have found.

Samples

3
35
4
2
4
35

2

Resources

厦门大学第四届程序设计竞赛 现场决赛