var
	x,y,n,s,a:real;
begin
	read(x,y,n);
	s:=x+y;
	s:=s*0.9;
	a:=n-s;
	write(a:0:1);
end.
	
/**************************************************************
	Problem: 1598
	User: admin
	Language: Pascal
	Result: Wrong Answer
****************************************************************/