Help with USACO 2015 Speeding Ticket

Debugging Help
#1

Problem Info

USACO 2015 December Contest, Bronze Problem 2 Speeding Ticket

USACO
http://www.usaco.org/index.php?page=viewproblem2&cpid=568

My Work

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;

public class Speeding {
    static int getMax(int[] arr) {
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] >= max) {
                max = arr[i];
            }
        }
        return max;
    }
    static int getSpeed(int mi, ArrayList<Integer> marks, ArrayList<Integer> speeds) {
        // getting speed with the mile and the corresponding speed
        int ind = -1;
        int curr = 0;
        for (int i = 0; i < marks.size(); i++) {
            ind++;
            curr += marks.get(i);
            if (marks.get(i) >= mi) {
                break;
            }
        }
        return speeds.get(ind);
    }
    static int getDiff(int mi, ArrayList<Integer> limits, ArrayList<Integer> limitmarks, ArrayList<Integer> speeds, ArrayList<Integer> speedmarks) {
        return getSpeed(mi, speedmarks, speeds) - getSpeed(mi, limitmarks, limits);
    }
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(new File("speeding.in"));
        PrintWriter pw = new PrintWriter("speeding.out");
        int n = sc.nextInt();
        int m = sc.nextInt();
        ArrayList<Integer> limits = new ArrayList<Integer>();
        ArrayList<Integer> limitmarks = new ArrayList<Integer>();

        ArrayList<Integer> speeds = new ArrayList<Integer>();
        ArrayList<Integer> speedmarks = new ArrayList<Integer>();

        for (int i = 0; i < n; i++) {
            int x = sc.nextInt();
            int y = sc.nextInt();
            limitmarks.add(x);
            limits.add(y);
        }
        for (int i = 0; i < m; i++) {
            int z = sc.nextInt();
            int q = sc.nextInt();
            speedmarks.add(z);
            speeds.add(q);        
        }
        sc.close();
        int[] maxs = new int[100];
        for (int i = 1; i <= 100; i++) {
            maxs[i-1] = getDiff(i, limits, limitmarks, speeds, speedmarks);

        }
        int ans = getMax(maxs);
        if (ans < 0) {
            ans = 0;
        }
        pw.println(ans);
        pw.close();
    }
}

I basically look at every individual mile and get the speed difference
.

What I’ve Tried

I submit the code but failed 3 test cases. I’ve tried testing out random values but I have gotten the correct answer.

Question

I don’t know why the code works on 7 test cases but fails on 3 other.

#2