from random import randint
import sys
n = 20
A = [randint(-15, 15) for i in range(n)]
open("A.txt", 'w').write("\n".join(map(str, A)))
print("Первый список")
print ((", ".join(map(str, A))))
m=max(A)
negatives = []
for i in range(1, n+1):
  if A[-i] < 0:
    negatives.append(n-i)
    if len(negatives)>1: 
      break
if len(negatives) < 2:
  open("B.txt", 'w').write("Error")
  sys.exit(0)
item = A[negatives[1]]
for i in range(n):
  if A[i] == m: 
    A[i] = item
  if i == negatives[1]:
    A[i] = m
open("B.txt", 'w').write("\n".join(map(str, A)))
print ("Второй список")
print (", ".join(map(str, A)))