Place a marker on any number.
Spell this number moving up or down, right or left.
Remove  three and one.
Move the marker five times by going up or down, right or left.
Remove twenty and twelve.
Move the marker seven times by going up or down, right or left.
Remove eight and seven.
Move the marker three times by going up or down, right or left.
Remove four and eleven.
Look at prediction.
Magic happens!

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