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Beyonce has offered her American fans the chance to win free tickets to see her and Jay-Z "for life".

The catch? You have to commit to eating more vegan meals.

The offer - which Beyonce has shared with her 123 million Instagram followers - is for one fan only and has a 30-year time limit.

Beyonce is running the competition through the Greenprint Project - which highlights the positive effect veganism can have on the environment.

Fans can submit how many of their meals are plant-based and in return, get the chance to win 30 years worth of tickets.

Beyonce has long been associated with the vegan movement. The Vegan Society says she's helped make a plant-based diet something to aim for.

She's posted pictures of her food and encouraged fans to join her by opting for a plant-based diet.

Now she's offering fans the chance to watch her and Jay-Z on tour for life.

The competition is only open to those living in the US but will give tickets to the winner for up to 30 years - and they get to take a guest.

The Greenprint Project site says "we each have the potential to save our planet with our meal choices".

By inputting how many plant-based meals you eat, the site makes various environmental calculations for you.

For example, "by eating nine plant-based meals I could have the environmental impact equivalent to 14 trees absorbing harmful gases from the air in a month," it says.

The prize is estimated to be worth around $12,000 (£9,100), according to the competition website.

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