by steps
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000000
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7f7f7f
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00007f
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007f7f
828081 828081
828081
007fff 007fff
007fff
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00ff7f
868183 868183
868183
00ffff 00ffff
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898285
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90848a 90848a
90848a
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ff7fff
97868e 97868e
97868e
ffff00 ffff00
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ffff7f
ffffff ffffff
ffffff
9b8891 9b8891
9b8891