H. The Wisdom of Master Wei
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

In the ancient and majestic city of Shanghai, future stage of the ICPC World Finals, a young programmer named Kai dreams of achieving the mastery of his mentor, the legendary Master Wei.

One day, while debugging complex code at the Wild Goose Pagoda, Kai asked, "Master, your experience is as vast as the Yellow River. When will my programming journey be exactly half of yours?"

Master Wei, with an enigmatic smile, replied: "Little grasshopper, experience is measured by years of practice. I started programming in year $$$W$$$, and you started in year $$$K$$$. There will come an exact year when my years of practice will be double yours. Find that year, and you will find the clarity you seek."

Help Kai solve his master's riddle.

Input

The input consists of a single line with two integers $$$W$$$ and $$$K$$$ ($$$0\leq W \lt K \leq 10^9$$$), representing the year Master Wei started programming and the year Kai started, respectively.

Output

Print a single number: the year when the master's experience will be exactly double Kai's.

Examples
Input
1975 1995
Output
2015
Input
1989 2007
Output
2025
Input
0 1000000000
Output
2000000000