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Try to make the number 8528 using the digits 7, 7, 7, 7, 7, 7, 7, 7 (eight 7).
Rules:
Use all eight 7s exactly once.
Allowed operations: $+,−,\times,\div$,$x^y$ (exponentiation),$\sqrt{x}$ (square root).
Parentheses are allowed.
Anything else is not allowed such concatenation, factorials, floor...