应该是0-1背包问题吧 ：这样不知行不行。
public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);  int n  = Integer.parseInt(sc.nextLine());  int sum =0 ;  int[] data = new int[n];  for (int i = 0; i < n ; i++) {
        data[i]  = sc.nextInt();  sum +=data[i];  } int m  = sc.nextInt();   Arrays.sort(data);  if (m<0||data[0]>m||sum<m) System.out.println("-1");   int[][] dp = new int[n+1][m+1];   for (int i = 0; i <=m ; i++) {
        dp[0][i] = 1;  } for (int i = 0; i <dp.length; i++) {
        dp[i][0] = 1;  } for (int i = 1; i <n+1 ; i++) { for (int j = 1; j <=m ; j++) { if (j >=data[i-1]) dp[i][j]  = Math.max(dp[i-1][j],dp[i-1][j-data[i-1]]*data[i-1]);  else dp[i][j] = dp[i-1][j];    }
    }
    System.out.println(dp[n][m]); }