Exponentiation II Formatting Change

[TheGamingMousse]

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ok i think this file was named incorrectly? i have no clue, but im pretty sure it should be cses-1712.mdx and not cses-1095 (cuz that's Exponentiation I)

also i think using a variable for $10^9 + 7$ looks better cuz i think the current formatting looks a bit ugly