class Solution {
 public:
  int countNegatives(vector<vector<int>>& grid) {
    const int m = grid.size();
    const int n = grid[0].size();
    int ans = 0;
    int i = m - 1;
    int j = 0;

    while (i >= 0 && j < n) {
      if (grid[i][j] < 0) {
        ans += n - j;
        --i;
      } else {
        ++j;
      }
    }

    return ans;
  }
};