import java.util.Scanner;

public class N538
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		int[] b=new int[3];
		for(int i=0;i<3;i++){b[i]=sc.nextInt();}
		int b4=(int)Math.pow((b[2]-b[1]),2)/(b[1]-b[0])+b[2];
		System.out.println(b4);
	}
}