Permutation group. Show that the group has just three members of length 2 in cycle notation.

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Show that there are just three members of $S_4$ which have two cycles of length 2 when written in cycle notation.

I'm having trouble figuring out how I should test this. It seems dumb to write out all 24 permutation combinations and then convert them to cycle notation.

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Assuming (and we can. Why?) the cycles are pairwise disjoint, it is clear the only such elements are $\;(12)(34),\,(13)(24),\,(14)(23)\;$ .