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my &f =

    {(.base(2)~~m:g/1+|0+/)».chars.max}


say f 6;       # → 110                   → 2
say f 16;      # → 10000                 → 4
say f 893;     # → 1101111101            → 5
say f 1337371; # → 101000110100000011011 → 6
say f 1;       # → 1                     → 1