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≤A,P≤100
Input
Input
Input is given from Standard Input in the following format:
AP
Output
Output
Print the maximum number of apple pies we can make with what we have.