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Boxed meals in Taiwan are very common, offering convenient and affordable nutrition-balanced choices for students and office workers. These meals typically include a variety of vegetables, protein, and rice, providing a well-rounded diet. With numerous options available at local self-service restaurants, they are a popular choice for those looking for a quick, healthy lunch.

There are five Taiwanese self-service restaurants numbered from 1 to 5. You plan to visit a different restaurant each day from Monday to Friday to pack a boxed meal for lunch. You've already visited one restaurant from Monday to Thursday, each time visiting a different one. Now, it's Friday, and you want to visit the last remaining restaurant that you haven't been to yet this week.

Write a program that takes as input the four restaurants you've already visited (one for each day from Monday to Thursday) and outputs the restaurant you should visit on Friday.

Input format:
A single line of input containing four integers $$$a, b, c, d$$$, each between 1 and 5 (inclusive), representing the restaurant numbers you visited from Monday to Thursday, in order.

- $$$1\le a, b, c, d\le 5$$$
- All four numbers will be different.
Output format:
Output the restaurant number you should visit on Friday.
Example Input 0:
1 3 2 5

Example Output 0:
4

Example Input 1:
2 5 4 3

Example Output 1:
1



Example input:
1 3 2 5

2 5 4 3


Example output:
4

1