CYRUS MCCRIMMON / Denver Post via Getty Images A Chipotle burrito in it's signature aluminum wrap .

Most people’s 20th birthdays aren’t all that memorable; so close to 21, but still not quite there. The chain restaurant Chipotle, which has faced slowing growth recently, is aiming to make its 20th anniversary more noteworthy with a massive online contest and free burrito giveaway. The grand prize: free burritos for 20 years for 20 winners.

Starting July 13th at 10:20 p.m. E.T., the contest involves solving 20 puzzles–one a day–with questions ranging from Chipotle history to food sustainability. Hints will come in the form of haikus. For the first 19 days, Chipotle will give away free burritos for a year (one a week) to 20 contestants each day via lottery. After completing the previous 19 trivia questions, the 20th day is when the grand prize will be awarded to the first 20 players who finish the final puzzle first.

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It’s a marketing gimmick, for sure, but the once-fast-growing company may be hoping the promo will help boost sales this summer. According to Businessweek, “the popular Mexican brand’s growth shows signs of slowing after 20 years—in the first quarter, same store sales went up only 1 percent, compared to 12.7 percent in the first quarter of 2012.”

The lucky winners of the grand prize will each save about $9,000 to $10,000 in burrito costs. That’s significantly more than the few pennies the chain was caught adding to some customers’ bills in an attempt to avoid time wasted counting pennies at the checkout counter. Last year, TIME reported that Chipotle was rounding totals–either up or down depending on the price—in New Jersey, New York, Boston and other high traffic restaurant locations in order to pull more customers in by cutting time spent at the cash register.

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