Null point exception help please

Question

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.*;

public class Starter{

    public static void main(String[] args) throws Exception {
        BufferedReader fh =
                new BufferedReader(new FileReader("iot.txt"));
        //First line contains the language names
        String s = fh.readLine(); 
        List<String> langs =
                new ArrayList<>(Arrays.asList(s.split("\t")));
        langs.remove(0);    //Throw away the first word - "week"
        Map<String,HashMap<String,Integer>> iot = new TreeMap<>();
        while ((s=fh.readLine())!=null)
        {
            String [] wrds = s.split("\t");
            HashMap<String,Integer> interest = new HashMap<>();
            for(int i=0;i<langs.size();i++)
                interest.put(langs.get(i), Integer.parseInt(wrds[i+1]));
            iot.put(wrds[0], interest);
        }
        fh.close();
        HashMap<Integer,HashMap<String,HashMap<String,Integer>>>
            regionsByYear = new HashMap<>();
        for (int i=2004;i<2016;i++)
        {
            BufferedReader fh1 =
                    new BufferedReader(new FileReader(i+".txt"));
            String s1 = fh1.readLine(); //Throw away the first line
            HashMap<String,HashMap<String,Integer>> year = new HashMap<>();
            while ((s1=fh1.readLine())!=null)
            {
                String [] wrds = s1.split("\t");
                HashMap<String,Integer>langMap = new HashMap<>();
                for(int j=1;j<wrds.length;j++){
                    langMap.put(langs.get(j-1), Integer.parseInt(wrds[j]));
                }
                year.put(wrds[0],langMap);
            }
            regionsByYear.put(i,year);
            fh1.close();
        }

        int count = 0;

        for(String week:iot.keySet())
        {
            if (iot.get(week).get("C++")>iot.get(week).get("C#"))
            {
                count = count+1;
            }

        System.out.println("The number of weeks that there was more interest in C++ compared to C# is: "+count);
    }
  }
}

This is my code, at the moment i get a java.lang.NullPointerException error on the line "if (iot.get(week).get("C++")>iot.get(week).get("C#"))"

I know that this is pointing to the week variable but i just don't understand why. I have used this same block of code (without the count) before and it worked fine so why after adding count in does it stop working?

Does anyone have any solution to fix this?