Fourier base - not as you know it!
A natural number \(n\) is called unfoury if in any natural base \(b\), none of the digits of \(n\) is four. E.g. \(1\) is unfoury. There exists a largest unfoury number \(M\).
Find \(N\) and \(M\). Your answer will be of the form \(N.M\) (with a decimal point between them). E.g. if you think that \(N=4\) and \(M=1\) then you should enter \(4.1\).
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