<s>[INST] What was the longest-standing incorrect proof of the Four Color Theorem in graph theory? [/INST] The first flawed proof, published in 1879 by A.B. Kempe, already contains an essential element of many later proof attempts with the so-called Kempe chains. The error in this proof was not discovered until 1890 by P.J. Hea-wood.</s>\ <s>[INST] what year was it finally proved [/INST] 