package yukicoder;

import java.util.Scanner;

public class No538 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[] b = {sc.nextInt(), sc.nextInt(), sc.nextInt()};
        double r, d, keisu;

        keisu = 1.0 / (b[1] - b[0]);
        r = keisu * b[2] + -keisu * b[1];
        d = keisu * -b[0] * b[2] + keisu * b[1] * b[1];

        System.out.println((int)(r * b[2] + d));
    }
}