Organizing Containers of Balls

string organizingContainers(vector<vector<int>> container) {
    unordered_map<int, int> mp;
    int m = container[0].size();
    vector<int> counter(m, 0);
    for(auto& c : container) {
        int sum = 0;
        for(int i = 0; i < m; i++) {
            sum += c[i];
            counter[i] += c[i];
        }
        mp[sum]++;
    }
    for(int i = 0; i < m; i++) {
        if(!mp[counter[i]]) return "Impossible";
        mp[counter[i]]--;
    }
    return "Possible";
}