import java.util.Scanner;

public class No538 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long b1 = sc.nextLong();
		long b2 = sc.nextLong();
		long b3 = sc.nextLong();
		long rbunbo,rbunshi,d;
		rbunbo = b2 - b1;
		rbunshi = b3 - b2;
		d = b2 - b1 * rbunshi / rbunbo;
		
		System.out.println(b3 * rbunshi / rbunbo + d);
	}
}