vector<vector<pair<int,int>>> prefix_sum(n+1, vector<pair<int,int>>(m+1, mp(0,0)));
    vector<vector<int>> gridsum(n+1, vector<int>(m+1, 0));
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            int x=arr[i][j];
            prefix_sum[i][j].first=prefix_sum[i-1][j].first+x;
            prefix_sum[i][j].second=prefix_sum[i][j-1].second+x;
            gridsum[i][j]=gridsum[i-1][j-1] + prefix_sum[i][j].first + prefix_sum[i][j].second - x;
        }
    }