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  "body": "\n## Statement\n\nLet $G$ be a finite loopless [[planar graph|029JQEK15B]].\nThen $\\chi(G) \\le 4$.\n\n## Remarks\n\nIn terms of maps: four colours are enough for the regions of a map in the plane. Regions with a common boundary segment get different colours.\nThe bound is sharp, because $K_4$ is planar and $\\chi(K_4) = 4$.\n\n## History\n\nFrancis Guthrie stated the problem in 1852.\nKenneth Appel and Wolfgang Haken proved the theorem in 1976, with the help of a computer.\nRobertson, Sanders, Seymour and Thomas gave a simpler proof in 1997. Georges Gonthier and Benjamin Werner checked a proof in the Coq proof assistant in 2005.\n\n## Explanations\n\n### L1 human\n\nFour colours are enough to colour any map, so that neighbouring countries always have different colours.\nIt was the first major theorem whose proof needed a computer.\n",
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