import clr
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *
import sys
sys.path.append('c:\\Program Files (x86)\\IronPython 2.7\\Lib')
import random

list1=[]
list2=list('ABCDEFGHIJKLMNOPQRSTUVWXYZ')
list3=list('abcdefghijklmnopqrstuvwxyz')

for i in range(IN[0]):
    a=str(random.randint(0,9))
    list1.append(a)
for i in range(IN[0]):
    a=random.randint(0,IN[0]-1)
    b=random.randint(0,25)
    c=random.randint(0,25)
    list1[a]=list2[b]
    a=random.randint(0,IN[0]-1)
    list1[a]=list3[c]

OUT=list1