What's wrong with my binary search?

Debugging Help
#1

Problem Info

https://cses.fi/problemset/task/1091

Question

Include a specific question if you have one.
Is there something wrong with my binary search?

What I’ve Tried

I have tried downloading the test data and test but still can’t find the problem.

My Work

#include<bits/stdc++.h>
using namespace std;
 
#define ll long long
#define fastio ios_base :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
 
int n, m, cnt = 1, sl;
 
int main() {
    fastio; cin >> n >> m;
    int price[n], maximum[m], dem[n];
    for(int i = 0; i < n; i ++) cin >> price[i];
    for(int i = 0; i < m; i ++) cin >> maximum[i];
    sort(price, price + n); vector <int> arr;
    for(int i = 1; i < n; i ++) {
        if(price[i] != price[i - 1])
            dem[sl ++] = cnt, cnt = 1, arr.push_back(price[i - 1]);
        else 
            ++ cnt;
    }
    dem[sl] = cnt; arr.push_back(price[n - 1]);
    for(int i = 0; i < m; i ++) {
        int l = 0, r = arr.size() - 1, ans = -1, pos = -1;
        while(l <= r) {
            int mid = (l + r) / 2;
            if(arr[mid] <= maximum[i]) {
                if(ans < arr[mid] && dem[mid] > 0)
                    ans = arr[mid], pos = mid;
                l = mid + 1;
            } else {
                r = mid - 1;
            }
        }
        if(ans > -1)
            -- dem[pos];
        cout << ans << '\n';
    }
}

Add explanation of code here : 
I count the appearance of every member than store the sorted price members into the arr only once for each member. Then i use binary search to find the ticket which largest value does not exceed the maximum money that a person is willingly to spend to the ticket.