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The diagram shows nine numbered counters 1 to 9 in order. Consider exchanging any two counters. For example swap 7 & 8. Then 8 & 4, 4 & 6, 6 & 9, 9 & 3 and 3 & 2. With these six exchanges we arrive at the number 139,854,276 which is the square of 11,826. This puzzle is to arrive at a square number in the same fashion in the least number of exchanges.
Cinelli