negative number

class Solution {
public:
    int countNegatives(vector<vector<int>>& grid) {
    int ans=0;
     for(auto u : grid)
     {
         reverse(u.begin(),u.end());
        int l=lower_bound(u.begin(),u.end(),0)-u.begin();
         ans+=l;
     }
        return ans;
    }
};