s = input().split()
x = int(s[0])
y = int(s[1])
a = x - 1
print("%.1f" % (a * 2.5 + y * 1.5))

/**************************************************************
	Problem: 1603
	User: admin
	Language: Python
	Result: Accepted
	Time:107 ms
	Memory:34244 kb
****************************************************************/