(Mercury). As for the determination of stepsize， we partly follow the previous numerical integration of all nine planets in Sussman & Wisdom (1988， 7.2 d) and Saha & Tremaine (1994， 225/32 d). We rounded the decimal part of the their stepsizes to 8 to make the stepsize a multiple of 2 in order to reduce the accumulation of round-off error in the computation processes. In relation to this， Wisdom & Holman (1991) performed numerical integrations of the outer five planetary orbits using the symplectic map with a stepsize of 400 d， 1/10.83 of the orbital period of Jupiter. Their result seems to be accurate enough， which partly justifies our method of determining the stepsize. However， since the eccentricity of Jupiter (∼0.05) is much smaller than that of Mercury (∼0.2)， we need some care when we compare these integrations simply in terms of stepsizes.
In the integration of the outer five planets (F±)， we fixed the stepsize at 400 d.
We adopt Gauss' f a
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