class Solution {
public:
    int leastBricks(vector<vector<int>>& wall) {
        unordered_map<int, int> h;
        for (auto& layer : wall) {
            int s = 0;
            for (int b : layer) {
                s += b;
                ++h[s];
            }
            h[s] = 0;
        }

        int cnt = 0;
        for (auto& [k, v] : h) {
            cnt = max(cnt, v);
        }
        return wall.size() - cnt;
    }
};