{"problem":{"name":"RGB Triplets","description":{"content":"We have a string $S$ of length $N$ consisting of `R`, `G`, and `B`. Find the number of triples $(i,~j,~k)~(1 \\leq i < j < k \\leq N)$ that satisfy both of the following conditions: *   $S_i \\neq S_j$,","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc162_d"},"statements":[{"statement_type":"Markdown","content":"We have a string $S$ of length $N$ consisting of `R`, `G`, and `B`.\nFind the number of triples $(i,~j,~k)~(1 \\leq i < j < k \\leq N)$ that satisfy both of the following conditions:\n\n*   $S_i \\neq S_j$, $S_i \\neq S_k$, and $S_j \\neq S_k$.\n*   $j - i \\neq k - j$.\n\n## Constraints\n\n*   $1 \\leq N \\leq 4000$\n*   $S$ is a string of length $N$ consisting of `R`, `G`, and `B`.\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$N$\n$S$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc162_d","tags":[],"sample_group":[["4\nRRGB","1\n\nOnly the triplet $(1,~3,~4)$ satisfies both conditions. The triplet $(2,~3,~4)$ satisfies the first condition but not the second, so it does not count."],["39\nRBRBGRBGGBBRRGBBRRRBGGBRBGBRBGBRBBBGBBB","1800"]],"created_at":"2026-03-03 11:01:13"}}