The hardest part: Goldbach's conjecture, known as "the jewel in the crown of mathematics", that any even number greater than 4 can be written as the sum of two odd prime numbers, abbreviated as 1+ 1, is not the hearsay retarded problem of "why one plus one equals two".

Goldbach conjecture has not been proved so far. People weaken it to the conjecture that any even number greater than 4 can be written as the sum of the products of m odd prime numbers and n odd prime numbers. People's goal is to reduce the values of m and n until m = n = 1. At present, the best result is obtained by China mathematician Chen Jingrun, who proved 1+2.