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PowerMod

compute a modular power efficiently
Syntax 

PowerMod(A:INT, B:INT, M:INT):INT

Description
This function calculates efficiently an integer power modulo a given modulus. Thus PowerMod(A, B, M) is equal to Mod(A^B, M), but the former is computed faster. B must be non-negative.

Example 
  PowerMod(12345,41041,41041); -- 41041 is a Carmichael number
12345
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  PowerMod(123456789,987654321,32003); -- cannot compute 123456789^987654321 directly
2332
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