def palindrone(s):
    left,right=0,len(s)-1
    while left<right:
        if s[left]!=s[right]:
            return False
        left=left+1
        right=right-1
    return True

s=raw_input()
l=len(s)
if palindrone(s):
    print s[:(l/2)]+s[(l/2)]+s[(l/2):]
    exit()
left, right=0,len(s)-1
while left<right:
    if s[left]!=s[right]:
        c1=s[:left]+s[right]+s[left:]
        if palindrone(c1):
            print c1
            exit()
        c2=s[:right+1]+s[left]+s[right+1:]
        if palindrone(c2):
            print c2
            exit()
        print "NA"
        exit()
    left=left+1
    right=right-1
print "NA"