Java solution for problem D

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Scanner;

public class big_maximum_sum_ahmed_java_ac {
    static int n, m;
    static long[] gen = new long[50], lft = new long[50], rght = new long[50],
            tot = new long[50];

    public static void main(String[] args) {
        BufferedReader bfin = new BufferedReader(new InputStreamReader(
                System.in));
        BufferedWriter bfout = new BufferedWriter(new OutputStreamWriter(
                System.out));
        Scanner cin = new Scanner(bfin);
        PrintWriter cout = new PrintWriter(bfout);
        n = cin.nextInt();
        m = cin.nextInt();
        int len, num;
        for (int i = 0; i < n; i++) {
            len = cin.nextInt();
            int mx = -(1 << 30);
            int sum = 0;
            for (int j = 0; j < len; j++) {
                num = cin.nextInt();
                tot[i] += num;
                lft[i] = Math.max(lft[i], tot[i]);
                rght[i] = Math.min(rght[i], tot[i]);
                mx = Math.max(mx, num);
                sum += num;
                if (sum < 0)
                    sum = 0;
                else
                    mx = Math.max(mx, sum);
            }
            gen[i] = mx;
            rght[i] = tot[i] - rght[i];
        }
        long cur = 0;
        long best = (long) (-1e18);
        while (m-- > 0) {
            int i;
            i = cin.nextInt();
            i--;
            best = Math.max(best, gen[i]);
            if (cur > 0)
                best = Math.max(best, cur + lft[i]);
            cur = Math.max(0, Math.max(rght[i], cur + tot[i]));
        }
        System.out.println(best);
        cout.close();
    }
}