import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner s = new Scanner(System.in); String[] str = s.nextLine().split(" "); s.close(); double b1 = Double.parseDouble(str[0]); double b2 = Double.parseDouble(str[1]); double b3 = Double.parseDouble(str[2]); double r = (b3 - b2) / (b2 - b1); double d = (b2*b2-b1*b3)/(b2-b1); double b4 = r*b3 + d; System.out.println((long)b4); } }