function f=fenceDem(infile, outfile)
%open infile for read
in = fopen(infile,'r');
%open outfile for write
out = fopen(outfile, 'w');

%get input from infile
%the values are in vector y and the total number of values is in "count"
[y, count] = fscanf(in, '%d', inf);

%calculate all pairs (using for loop)
for i=1:1:count/2
    W = y(2*i-1);
    A = y(2*i);
    
    % we know
    % WL + 0.5*D^2 = A,  and
    % W=sqrt(2)*D
    % so we have   WL + 0.25*W^2 = A
    % solve this equation and we get
    L = (A-0.25*W^2)/W;
    
    %output the L value to outfile
    fprintf(out, '%f\n', L);
end

%close all the files we opened
fclose(in);
fclose(out);