s = input().split()
x = float(s[0])
y = float(s[1])
z = float(s[2])
su = 8.5 * x + 5.6 * y + 6.2 * z
print('%.1f' % su)
/**************************************************************
	Problem: 1610
	User: admin
	Language: Python
	Result: Accepted
	Time:128 ms
	Memory:34244 kb
****************************************************************/