12
21
there are 2 outcome which is 2! not 2x2

do it for 3

123
132
213
231
312
321

6 options which is 3! not 3x3

this is also true for 4

1234 2134 3124 4123
1243 2143 3142 4132
1324 2314 3214 4213
1342 2341 3241 4231
1423 2413 3412 4312
1432 2431 3421 4321

24 outcomes with is 4! not 4x4

thus it is 6! not 6x6

so your answer is 720

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