(F R U R' U' F')(f R U R' U' f')

(R U2 R) (R F R F') U2 (R' F R F')

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(f R U R' U' f') U (F R U R' U' F')

(F R' F') (R U R U' R') U (F R U R' U' F')

(F R' F') (R U R U' R') U' (F R U R' U' F')

(R U R' U) (R' F R F') U2 (R' F R F')