6_1.js

const input = 'bfdbbngnvnsvshhhrvrbrtbrrhqrqgrrmmdfmmqttptltntrntrnrcrdcrrctctdtwtrwwmlltcltcllmpprvvtbbmbvbsvvqwvvscswsqqgzqqppvzppnddjwddlrdlllmwllfccdfccswwrhhndhdhfdftdfdcdcllcjjbsbgssvlvrrhfrfjfpjffvnfvfwfzftztwwrhwrhwhwddpjjmhmgmsssstzszqzfqzzprpzpnndttphtpphvvcpcjppdtdwwqgwwwnhwnnvhvsvqqtrrbsscwssgwglgwlldjdzjjbsjbsbvvpbvppvfvqvbqbzzwtwbwpbbbcffdgggpnpfptpfphfhfthfthffzrrbzbcblbmmzmhhnvvqvlvwvzvtztgzznbbcqbccwhcwcnwnhndhhgcghhlthllplvppgngrgsswfsfnfjjswstsrtrhthhqzqggdtggzvvjljddqdzzrmrjmjcmjmrrwlldttrhhfjjgbglgjlldrllppnwpnwnndrddtdqdhhpccbgcgzzswzztgzzrwwzzmtztvvrtrgttvddwvwvmwvmmdjdrdtthqhgqhggldgdfdnnzjnjffmrrnprnpnssjrrbrjjrrzvrvhvllfvlvnlvvhlhrhzrzrsrswrssjvjdjfjwwjmjvjjthhnjnmnppsccmlcclfclcbllldwldwdlwddbddmnmrmgrmmtsszgssqjsqscswwzmwmbwwvqqbtbtwwpbbwdbdbhhqmqgqddflfmfnmffbtfbbsdsffspsjpsspzszccrsrstrtjrjppcrrpqqvttsbbjtbjjpbbccmzznvvzzvnvmmwmhmvmsstlssqtssvggtbgttgvtggfhggbcgcmcrmcmhhbttdlttfrfprrvttrtggcpplccqggcwwdjjjplprrbsrbbjsjbbfhbhphtttpffdgdgjddzldzlzplpnplljttdqqlmlllhzhjhccpwcwhwwbbqtqffjpfpfpjptplltbtzbbwwvggpcpprdprpbpvvgzgczzfffzcfzccjffrmrhmrhhchvhddsvswscsnnpfppdrdcrdrgdgmdgmgllhggjwggvqvmmvrrzpprhhqfhfvffvlvnlngnffbbtccfbfhfwhhhhwcwzwjjbffvrffqrrnsnwswrsrvrjvrvprpsptspttbztzfzlfzlflcflclqlplglmlqqvlvvhccmmddqvqzvvmlllvnlnhnfnwnlndnntrrhvvgjjnpnggfqgqdqqzvvclvclvlfvlvvlzlssqffmrfmfmjjczcmmmnttnfnmfnmmmhmggjgdjjqmjjvsslszlzrrpdpcpfcpfpnpssvtsvtvllbttzzljzzhrrnsnddjgdjgjljzzvhvddmdvvdtdmmpmqmnnwcwfwbfwwsvvbpvvgvnvcvdvtvrrcppwbppcqpccwqqzmqmmzczppwbbrzrjzzcrcvrrpttrjjcdjcjfcclscstthqhfqhffdcfdfqdqldddsswbblppdmdnnjvvhwvhvjhvjhjhlhcclrrcqcgcjgcjjtbtctbcbsccfwwltlrlplpfpjphplhhgtghhrppwhhrprwpwhhdqdpdwpwwtccvncvvvrpvphpssfpplcczttltgltldlmlqmmbsszdszznpprsprsprsppsbppjddjhhnrrfsrffmlmglgmlglccddpssdpsddhhfmfsfrfsfnnlggfrgghmgmrmprmprrnvrnnbqnqddhhfwfmfwfmfpfdfzdzppsbpsbpprfrvvwvtwtltvlttrhhgvhhjttmssdggnzzvmvcczmzbzwzttvtpvpcphcctmmhshjsjbssglsglgtltslscchhhsjjpljjdtdsdpppptlpprmppwdppglgmggnddztdzddzppswwmhfbpqzffjqgmsntwsnrwqrqwgpwgrbpbjwrhbcdcvqjnwslsnwhglcsjbwjhswjvzssfqgwbbdgbwfrblfmmlmsndhtlbwzfwsspqlncspqbgbnzshbwpvrmjqjzbcbzzdgssbtqdzffjphqjvrspfrjhpspbwcjwbfhqzsdnjwqjzjtjgnbrdbwqhzffphzppvlmsmppqcfjbjbdsnbwtvthwqcfrtfrwchnmqmhnwfcjtbwqwwvlnpmwlrvzwljrljzqstzglqwbzfdftzltlcbvmmfwcjqglvznztwnvzvftpndqmngqswppsnqhdbgthrddfbcfpflpndrhmcqwvnbfztsvnjjdwqgpmvdwvdftgbtvrwbnvvrwsdfzhwbwdhlpzbcqdzhbfqtpjqcmrpvcsrmcwvgghqrclfzpfgnppzmhvdhvdfrcrnjbdcwbftcqjhhfdsnfnwjzjllzzqftzsjrqnsbpjdcswhhmwwdzmvmqcjtqnczjcvzmmqwzjhjpcczgpbmcvbwmpmvnghlrgcmrrdnmjvmvnhtpfpgwgmdfzvlbclzjzwdqqcvfhhgfzdhzpdvfmwjlzzrpdgzmttmvvcplbwfzqftcgcwcgcpgwvnmlqsplpqwfnhwvqtlwcspqdzshsqnlcpqhpcpbwdhdjsmvtbqdwbcrscqfjcrcjhbjbpzbshpbmlcthmbjfwhzfphgbfqfnfztptzvdnwrpslmdtpmzmpbsszqshwdghrbtvhwzhcmpcgfqggpgzwmhhdrlhlvnpzvwwhzqvgvhrzngttcnqgjjhnblncnqnjzlwnmwnrtvwjtnrbhthncwmzwqdbdgtwrncljddnbhmphgjzfrrgmmcwfwjwjlcrhvcdtvsrvsfhmlgmzsgjchhrfmqslmdgtdtrlbhdffddvbsdbdwlwdcmcmmpvzpdtmbthjdzlpwftptpfsggmhjfjwvbwljsfhfwtbfwmczwhbmhvzllqtcqqfbrcdqqsrcpfmnswnfzfqghcmcbqwgvzqpwvvmbpddlhgjgzvgmpljznrhqphwcztqzpnhzqdgpwwclmsgpwnwtvtsjsdmcnvmjbqglttrhbzqdbgwnbsqzmsmztndrtmlpszhzgjbbftbsdwwdrlftrbbnrsqshfhdpdrwmztcqzdjlnthnjhppwntmbqdgzpmfmfnccblsdwljqhjfgtlgvpzpjbsndmwzfwrbmdhpnmbchqlwqtbhhhqqbsfnvscjwrzvjdtvbsqwzvfhwbbjgqpzcwqjdrlfmggzmhbcrhtbqdjntbtqdvmvpqflmccfpnbmnmtqbdflsgczpbsqpfphlzqgvwbjlmsgshrhpcljzdvwvdvlqqwchtjmjgtqjhgwtnddmhphwhvwhtrhfbjjjzfgrcqngnnddctzdzlqjlbdwmjqzccwrvctrzgtzqsswggbqdnplclhtdslcvzhppcjjslnshtwjnbrwdprqhdtfqmqpgfgnqtdnnhrnzfrsqhlftpdslgmmvqhvpjqjwpwgtnmgrbhwntdjftfwtjzjtprctbtsjmqmpcbbtrjvsgqgsfjprqmsmdztbhnbgzldqfzgwqwnnccgcfclctrwqmqpgvfglgsmmpjszqnphnzcnvswpsfsrmnsnlqnpmvfdvdtfgzrdmbftdrrrbfsvzfgmnffvjpcpnndrwhtjjrrvnztlfhcvfqjgfrhtbnhmwnrmwdhzmmtvjmsqmghtbtfjwdnvdcqtqjrfhrwscjftmbgjmcsrbpdpttlmvfmnfjhnptqvggnshzqnlqqdpqqsqssppbwpblhgfrwrblpzwvqphpsgfmbpqtqqpjpgnbblzstgcjhqntgpbfwlzzctqbnbvpgwsdsdldqzhvznqcsrrghpwllshqpdlqnqgzfwrnhwsvhftzplspcbqmclplprlthvwjhdndrjblqdgwvgjlbmblbmcnbzwzdlnpnhhppvrtngvqqwsttgwlvtcqmtrvpbnvcnfqdtqrsrsmhclmtgbdwwdvhwgfcqpmprcpdhqwftcchbwvstcdqrlwtgbcfqfgzprgvpbbzlqfzbqtcrlzscnqpqwtgzbbbdvsvmhggdr';

console.log(input.split('').reduce((previousBufferObject, currentChar) => previousBufferObject.found || (!previousBufferObject.bufferString.split('').some((char, index, charArray) => charArray.lastIndexOf(char)!=index) && previousBufferObject.bufferString.length === 4) ? {...previousBufferObject, found: true} : {bufferString: previousBufferObject.bufferString.slice(-3) + currentChar, count: previousBufferObject.count + 1, found: false}, {bufferString: '', count: 0, found: false}).count);