Vault password

Question: 28th Feb, 2015 Josh went to rob a bank. He threatened to kill the cashier if he didn't open the vault. The cashier told him the vault is not opened with keys but with a password. You can't kill me since I'm the only one who knows the password and everyday the password is different. Josh shot the cashier, entered the password, opened the vault and stole all the money. What is the password?

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