Simply follow these instructions:

  1. Pick a positive integer n that is bigger than 1 but still fairly small and suits you.

  2. Legibly write the integers from 1 to n(n+3)/2 either in a column if that many won't fit in a row or else in a row if they will.

  3. Repeat n times: Cross off your choice of EITHER the first uncrossed number from the beginning of the row or column OR the first uncrossed number from the end.

  4. Sum the numbers you crossed out, but use a calculator because this trick isn't something where obnoxious mental calculation is something you should bother with.

  5. Divide this sum by n(n+1)/2 to get a new number which we will call "the".

  6. Start at the first uncrossed number in your row/column (as 1) and count numbers in the row/column until you get to the "the"th number.

  7. Subtract n from the number you just stopped counting on, but do it in your head this time because typing into the calculator would just be a waste of effort for this one.

  8. Read the last words in each of instruction 1 through 7 for my prediction.