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states = ('q0', 'q1', 'q2')
start = 'q0'
accept = ('q0',)
s = input()
# start with the start state, use the transition function...
currentState = start
for currentLetter in s:
    # transition function in here, can only use current input symbol and
    #  current state
    # big 'ol if/elseif
    if currentState == 'q0' and currentLetter == 'a':
        currentState = 'q0'
    elif currentState == 'q0' and currentLetter == 'b':
        currentState = 'q1'
    elif currentState == 'q1' and currentLetter == 'a':
        currentState = 'q1'
    elif currentState == 'q1' and currentLetter == 'b':
        currentState = 'q2'
        
    elif currentState == 'q2' and currentLetter == 'a':
        currentState = 'q2'
    elif currentState == 'q2' and currentLetter == 'b':
        currentState = 'q0'
    else: print('THIS SHOULD NOT HAPPEN')
# do we accept or not
doIAccept = False
for x in accept:
    if currentState == x:
        doIAccept = True
        break
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