function meshBoundaries(V, F)

M = zeros(size(V,1));

for i = 1:size(F,1)
    if F(i,1)<F(i,2)
        M(F(i,1), F(i,2)) = M(F(i,1),F(i,2))+1;
    else
        M(F(i,2), F(i,1)) = M(F(i,2),F(i,1))+1;
    end
    if F(i,2)<F(i,3)
        M(F(i,2), F(i,3)) = M(F(i,2),F(i,3))+1;
    else
        M(F(i,3), F(i,2)) = M(F(i,3),F(i,2))+1;
    end
    if F(i,3)<F(i,1)
        M(F(i,3), F(i,1)) = M(F(i,3),F(i,1))+1;
    else
        M(F(i,1), F(i,3)) = M(F(i,1),F(i,3))+1;
    end
end

trisurf(F,V(:,1),V(:,2),V(:,3))

for row = 1:size(M,1)
    for col = 1:size(M,2)
       if M(row,col) == 1
          hold on;
          plot3([V(row,1); V(col,1)], [V(row,2); V(col,2)], [V(row,3); V(col,3)], 'r')
       end
    end
end


end

function printOff(filename)
    [V, F] = readOff(filename)

    trimesh(F,V(:,1),V(:,2),V(:,3))
    axis equal;
end

function [V,F] = readOff(filename)
    fid = fopen(filename,'r');
    str = fgets(fid);
    p = fscanf(fid,'%d %d %d\n', 3);
    V = fscanf(fid,'%f %f %f\n', [3 p(1)]);
    V=V';
    F = fscanf(fid,'%d %d %d %d\n', [4 p(2)]);
    F=F(2:4,:)+1;
    F=F';
    fclose(fid);
end

[V, F] = readOff('screwdriver.off')
meshBoundaries(V,F)