function total_sum = colsum(in)
if labindex == 1
    % Send magic square to other labs
    A = labBroadcast(1,in) 
else
    % Receive broadcast on other labs
    A = labBroadcast(1) 
end

% Calculate sum of column identified by labindex for this lab
column_sum = sum(A(:,labindex))

% Calculate total sum by combining column sum from all labs
total_sum = gplus(column_sum)