We have A apples and P pieces of apple.

We can cut an apple into three pieces of apple, and make one apple pie by simmering two pieces of apple in a pan.

Find the maximum number of apple pies we can make with what we have now.

Constraints

• All values in input are integers.
• $0 \leq A, P \leq 100$

Input

Input is given from Standard Input in the following format:

A P

Output

Print the maximum number of apple pies we can make with what we have.

Examples

Input

1 3

Output

3

Input

0 1

Output

0

Input

32 21

Output

58

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