Printing strings "a" to "zzzzz"

printing_strings

#  The task:

#  Print strings from "a" to "zzzzz" without using any loop or conditional statements. Don't just write all 1000 permutations out by hand. The output should look like this:
#  a
#  b
#  c
#  ...
#  aa
#  ab
#  ac
#  ...
#  zzzzx
#  zzzzy
#  zzzzz


### Full solution --- don't recommend you try running this
cat(sapply(letters, function(a) sapply(letters, function(b) sapply(letters, function(c) sapply(letters, function(d) paste(a, b, c, d, letters, "\n", sep=""))))))

### A sub-problem that will finish in a reasonable amount of time.  It prints "a" to "zzz".  
cat(sapply(letters, function(a) sapply(letters, function(b) paste(a, b, letters, "\n", sep=""))))