vector<string> cavityMap(vector<string> grid) {
    
    //Check if the grid is big enough for cavitys
    if(grid.size() < 3 || grid.at(0).size() < 3){
        return grid;
    }
    
    //Result 
    vector<string> result = grid;
    
    //Check for cavities
    for(int i = 1; i < (grid.size() - 1); i++){
        for(int j = 1; j < (grid.at(i).size() - 1); j++){
            if(grid.at(i).at(j-1) < grid.at(i).at(j) 
            && grid.at(i).at(j+1) < grid.at(i).at(j)
            && grid.at(i-1).at(j) < grid.at(i).at(j)
            && grid.at(i+1).at(j) < grid.at(i).at(j)){
                result.at(i).at(j) = 'X';
            }
        }
    }
    
    return result;
}