import java.util.ArrayList; import java.util.List; import java.util.Scanner; public class Main { 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 b0=c; int b1=c+b; boolean isAns=false; if(b0%a==0){ System.out.println(b0/a); isAns|=true; } if(b1%a==0){ System.out.println(b1/a); isAns|=true; } if(!isAns){ System.out.println(-1); } } }