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(NEXSTAR) — There’s one password San Francisco programmer Stefan Thomas probably should have memorized, and it’s standing between him and $240 million.

Thomas holds a small hard drive called an IronKey that contains the keys to a digital wallet containing 7,002 Bitcoin, the New York Times reported Tuesday. That amounts to exactly $242,546,164.27.

But Thomas can’t seem to figure out the password — and he only has two more chances to get it right. The IronKey only allows users ten guesses.

Thomas said he lost the paper where the password was written years ago. He’s already tried eight of his most commonly used passwords.

“I would just lay in bed and think about it,” Thomas told the Times. “Then, I would go to the computer with some new strategy, and it wouldn’t work and I would be desperate again.”

On Twitter, Thomas called the saga “a painful memory” and said he hopes “others can learn from my mistakes.”

“Test your backups regularly to make sure they are still working. An ounce of foresight could have prevented a decade of regret,” he said.

About 20 percent of existing Bitcoin appear to be in “lost or otherwise stranded wallets,” the Times reported. That amounts to around $140 billion.

A single Bitcoin at time of writing is worth more than $34,600, despite tanking in value earlier this week.

On Monday, Bitcoin fell more than 10 percent from the previous day. The cryptocurrency is up over 300 percent in the last 12 months.