Suzanne Alejandre
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Here's the problem:

There are seven stepping stones and six people. On the three lefthand stones, facing the center, stand three of the people. The other three people stand on the three righthand stones, also facing the center. The center stone is not occupied.
The challenge: exchanging places
    Everyone must move so that the people originally standing on the righthand stepping stones are on the lefthand stones, and those originally standing on the lefthand stepping stones are on the righthand stones, with the center stone again unoccupied. Can you find the least number of moves?
The rules:
  1. After each move, each person must be standing on a stepping stone.
  2. If you start on the left, you may only move to the right. If you start on the right, you may only move to the left.
  3. You may "jump" another person if there is an empty stone on the other side. You may not "jump" more than one person.
  4. Only one person can move at a time.
Try it!:

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