C++ - Answer is wrong when i include sort() function (Rudolf and the ticket from codeforces)?

so i was wondering why my code somehow gives the correct output only when i remove the 2 sort functions as the value themselves don't change?

The question

Also, I'm unable to post on code forces yet as I'm a beginner so i thought i could get help here. Thanks so much in advance!

My code:

#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int t;
    cin >> t;
    
    while(t--){
        int n, m, k, count = 0;
        cin >> n >> m >> k;
        int A[1000], B[1000];
        for (int i = 0; i < n; i++){
            cin >> A[i];
        }
        for(int i = 0; i < m; i++){
            cin >> B[i];
        }
        sort(begin(A), end(A));
        sort(begin(B), end(B));
        
        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                if(A[i] + B[j] <= k){
                    count++;
                }
                
            }
        }
        cout << count << endl;
    }
}

Can't figure out why it will only work when i remove sort function