There are n applicants and m free apartments. Your task is to distribute the apartments so that as many applicants as possible will get an apartment.
Each applicant has a desired apartment size, and they will accept any apartment whose size is close enough to the desired size.
Input
The first input line has three integers n, m, and k: the number of applicants, the number of apartments, and the maximum allowed difference.
The next line contains n integers a_1, a_2, …, a_n: the desired apartment size of each applicant. If the desired size of an applicant is x, he or she will accept any apartment whose size is between x-k and x+k.
The last line contains m integers b_1, b_2, …, b_m: the size of each apartment.
Output
Print one integer: the number of applicants who will get an apartment.
Constraints

1 less than or equal to n, m less than or equal to 2 * 10^5
0 less than or equal to kl ess than or equal to 10^9
1 less than or equal to a_i, b_i less than or equal to 10^9

Example
Input:
4 3 5
60 45 80 60
30 60 75

Output:
2

My attempt so far:

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int m;
    int n;
    int k;
    cin >> n >> m >> k;
    multiset<int> desired;
    multiset<int> actual;
    int input;

    for (int i = 0; i < n; i++)
    {
        cin >> input;
        desired.insert(input);
    }
    for (int i = 0; i < m; i++)
    {
        cin >> input;
        actual.insert(input);
    }
}

So far, I’ve taken the input of n, m, and k. I then took the second line of input which is the desired apartment sizes and stored them inside a multiset named desired. I then did the same with the actual apartment sizes and stored them inside a multiset named actual. I don’t know what to do from here :(. Can I have a hint on solving it please?