About 1500 years ago, Zu Chongzhi, a great mathematician in my country, calculated the value of π between 3.1415926 and 3.1415927, and became the first person in the world to accurately calculate the value of π to 7 decimal places. Modern people have used computers to calculate the value of π to more than 51.5 billion decimal places. The arrangement of these numbers is neither ordered nor regular. But careful students found that: the first 3 from the left is a prime number, 31 is also a prime number, but 314 is not a prime number, then in 3141, 31415, 314159, 31415926, 31415927, what is the prime number?
大约1500年前，我国伟大的数学家祖冲之，计算出π的值在3.1415926和3.1415927之间，成为世界上第一个把π的值精确到7位小数的人．现代人利用计算机已经将π的值计算到了小数点后515亿位以上．这些数排列既无序又无规律．但是细心的同学发现：由左起的第一位3是质数，31也是质数，但314不是质数，那么在3141，31415，314159，31415926，31415927中，质数是多少．
<result>314_159</result>