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&&c-b<=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);
        }
    }
}