Railroads require electricity?
300th
301st
302nd
303rd
304th
305th
306th
307th
308th
309th
310th
311th
312th
313th
314th
315th
316th
317th
318th
319th
320th
321st
322nd
323rd
324th
So the rule, in order of evaluation, is:
Ends in 11 -> th (Ie, two hundred and eleventh regiment).
Ends in 12 -> th (Ie, twelfth regiment).
Ends in 13 -> th (Ie, five hundred and thirteenth regiment).
Ends in 1 -> st (Ie, one hundred and first regiment)
Ends in 2 -> nd (Ie, six hundred and twenty second regiment)
Ends in 3 -> rd (Ie, Thirty third regiment)
Ends in * -> th (ie, fourteen hundred and seventeenth regiment)
Hope that helps!