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powTR x n = powTRh x n 1
        where
         powTRh _ 0 1 = 1
         powTRh _ 0 acc = acc
         powTRh x n acc = powTRh x (n - 1) $! (x * acc)

countDigitsTR n = countDigitsTRh n 0
            where
             countDigitsTRh n acc | (abs n <= 9) = acc + 1
                          | otherwise = countDigitsTRh (quot n 10) $! (acc + 1)