Pin Entry

The PIN is 2468. Read entries with the prompt PIN: (stripped) for at most three attempts, counted with attempts and stopped by the unlocked flag in the loop condition, without a break. An entry that is not all digits (.isdigit()) prints Digits only. and does not use up an attempt; a wrong PIN uses one and prints Wrong PIN, <n> left. where n is 3 minus the attempts used; the right PIN prints Unlocked.. After the loop print Card kept. on its own line when the user never got in. Input: one entry per line. Prompts are part of the output.