My guess, is that you forgot to take the *linear* nature of the $sp$ carbon-carbon bonds into consideration. So the bond lines cutting through four carbon atoms will be *linear*, and not *zig-zagged* as in the rest of the molecule (the latter implies tetrahedral geometry accorded by the $sp^3$ carbon-carbon bonds)

What you probably drew:

[![enter image description here][1]][1]

As opposed to what the skeletal representation for your molecule is *supposed* to look like:

[![enter image description here][2]][2]

<sub> Crude diagram courtesy: MS Paint application </sub>

<sub> Okay, it might be better if you draw the whole thing with the (lone) triple bond parallel to the bottom of your page (i.e- aligned with the horizontal) </sub>

The red circles represent the carbon atoms in your molecule. They (red-carbon-circles) aren't supposed to be drawn in, but I added it for clarity O:)


  [1]: https://i.sstatic.net/vpseE.jpg
  [2]: https://i.sstatic.net/lPNXU.jpg