s = input().split()
x = int(s[0])
y = int(s[1])
n = int(s[2])
a = (x + y) * 0.9
print(n - a)

/**************************************************************
	Problem: 1598
	User: admin
	Language: Python
	Result: Accepted
	Time:108 ms
	Memory:34244 kb
****************************************************************/