24 different four-digit numbers can be formed by using the four number cards of 1, 2, 3, and 4. If they are arranged in order from small to large, the first number is 1234, the second number is 1243, and the 15th number What is the number.
用l、2、3、4这四张数字卡片可以组成24个不同的四位数，如果把它们从小到大依次排列出来，第一个数是1234，第二个数是1243，第15个数是多少．
<result>3_214</result>