96

class Solution:
    # @param {integer} n
    # @return {integer}
    def numTrees(self, n):
        nums=[0]*(n+1)
        nums[0]=1
        for i in range(1, n+1):
            for j in range(1, i+1):
                nums[i]+=nums[j-1]*nums[i-j]
        return nums[n]