I've passed all of the user tests on here, and any test I can think of.
Still getting WA on #14.
Here's my non-working code.

import java.io.*;

public class P1998 {
    static StreamTokenizer in;
    static PrintWriter out;

    static int nextInt() throws IOException{
        do{
            in.nextToken();
        }while(in.ttype != StreamTokenizer.TT_NUMBER);
        return (int)in.nval;
    }

    public static void main(String[] args) throws IOException{
        in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        out = new PrintWriter(System.out);

        int n = nextInt();
        int m = nextInt();
        int k = nextInt();

        int[] stones = new int[n];
        int[] dropsTo = new int[n];

        int tmp = 0, j = 0;
        for(int i = 0; i < n; i++){
            stones[i] = nextInt();

            while(j < i - 1 && tmp - stones[j] > k){
                tmp -= stones[j];
                j++;
            }
            tmp += stones[i];
            dropsTo[i] = j;
        }

        j = 0;
        int moment, time = 0;
        for(int i = 0; i < m; i++){
            moment = nextInt() - time;

            time += moment;
            j += moment - 1;
            if(j >= n){
                time -= moment - n;
                j = n;
                break;
            }
            j = dropsTo[j];
        }

        out.println(time + n - j);
        out.flush();
    }
}