原代码 # give n,find x,x<n,x is first prime import math def is_prime(p): if p==2 or p==3: return 1 tn=int(math.sqrt(p))+1 for k in range(2,tn,1): if p/k==int(p/k): return 0 return 1 # - - modi under 1 line n=53 # ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ if n<4: print("The num <4, pro over.") exit(0) yes=1 if n%2==0: n=n-1 else: n=n-2 while n>=3: yes=is_prime(n) if yes==1: print("Key is",n," ,pro over.") break n=n-2