import java.util.Scanner;

public class Brother_chase {
    public static void log(Object obj) {
        System.out.println(obj.toString());
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int p = c;
        int q = c + b;
        boolean flag = false;
        if(p%a==0&&c-b<=0) {
            log(p/a);
            flag = true;
        }
        if(q%a==0) {
            log(q/a);
            flag = true;
        }
        if(!flag) {
            log(-1);
        }
    }
}