import java.util.*;
import java.util.Arrays;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a1 = sc.nextInt();
		int a2 = sc.nextInt();
		int a3 = sc.nextInt();
		int r =(a3-a2)/(a2-a1);
		int d = a2-r*a1;
		System.out.println(a3*r+d);
	}
}