Goldbach's conjecture is that: "every even number greater than 2 can be expressed as the sum of two prime numbers". Then, among the two prime numbers represented by 168, what is the number whose unit digit is 1?
歌德巴赫猜想是说："每个大于2的偶数都可以表示成两个质数之和"．则168表示成的两个质数中，个位数字是1的数是多少．
<result>71</result>