The ancient Mayan civilization used a vigesimal (base-20) numeral system.
The numerals are made up of three symbols; zero (egg shape), one (a dot) and five (a bar).
For example, 19 is
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Digits are stacked with the higher significant digits at the top, so
.
.
=
would be read as 1 11 in base 20 (one "twenties" and eleven "ones") or decimal 31.