class NumMatrix {
public:
    vector<vector<int>> grid ;

    int valid (int r , int c)
    {
        return r < grid.size() && c < grid[0].size() ? grid[r][c] : 0;
    }
    NumMatrix(vector<vector<int>>& matrix) {

       grid = matrix;

        for (int i = 0 ; i < grid.size() ; i ++ )
            for (int j = 0 ; j < grid[0].size() ; j ++)
                grid[i][j] += valid (i-1, j) + valid(i,j-1) - valid(i-1,j-1);
    }

    int sumRegion(int row1, int col1, int row2, int col2) {


       return valid(row2, col2) - valid(row1 - 1, col2) - valid(row2 , col1 - 1) + valid (row1 -1, col1 -1);

    }
};

/**
 * Your NumMatrix object will be instantiated and called as such:
 * NumMatrix* obj = new NumMatrix(matrix);
 * int param_1 = obj->sumRegion(row1,col1,row2,col2);
 */

/*




*/