方法：dp

就是输入两个整数m，x；x是总价，m是个数

第二行输入m个价格，问你m个价格中有几种方案相加等于x。

比如x=25，m=5， 第二行是：3，7，5，5，10，答案是两种，因为3+7+10=20，两个5算两种不同的方案

// We have imported the necessary tool classes.
// If you need to import additional packages or classes, please import here.

public class Main {
    public static void main(String[] args) {
    // please define the JAVA input here. For example: Scanner s = new Scanner(System.in);
        Scanner sc = new Scanner(System.in);
        int all = sc.nextInt(); //总价
        int cnt = sc.nextInt(); //个数
        int arr[] = new int[cnt];
        for(int i = 0; i < cnt; i++)
            arr[i] = sc.nextInt();
    // please finish the function body here.
        int dp[] = new int[all + 1];
        dp[0] = 1;
        for(int i = 0; i < cnt; i++){
            for(int j = all; j >= arr[i]; j--)
                dp[j] = dp[j] + dp[j - arr[i]];
        }
    // please define the JAVA output here. For example: System.out.println(s.nextInt());
        System.out.println(dp[all] != 0 ? dp[all] : -1);
    }
}