class Solution {
public:
    // placebo
    int bal[21] = {};
    int maximumRequests(int n, vector<vector<int>>& requests, int i = 0) {
        if (i == requests.size())
            return count(begin(bal), begin(bal) + n, 0) == n ? 0 : INT_MIN;
        --bal[requests[i][0]];
        ++bal[requests[i][1]];
        auto take = 1 + maximumRequests(n, requests, i + 1);
        ++bal[requests[i][0]];
        --bal[requests[i][1]];
        return max(take, maximumRequests(n, requests, i + 1));
    }
};