SAN FRANCISCO (CBS/AP) — A San Francisco man is attempting to run seven marathons in seven days on seven continents.

Thirty-one-year old Tim Durbin is the only American competing in the World Marathon Challenge that starts Saturday.

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The group starts in Antarctica, then it’s onto Chile, followed by Miami, Madrid, Morocco, Dubai, ending in Sydney, Australia.

On each of the seven days, Durbin and 8 others will aim to complete a 26.2 mile marathon.

Two in the group will try to run a half-marathon each day.

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The other competitors are from Brazil, India, Great Britain, Hong Kong, France, Finland and Australia. Many are seasoned marathoners.

Eleven have run the North Pole Marathon or Anatarctic Ice Marathon, the northernmost and southernmost marathons on earth.

Durbin also trying to raise $77,777 for a cancer research foundation. But he’s also shelling out $37,000 to participate.

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