{"problem":{"name":"Sandwiches","description":{"content":"You are given a sequence of positive integers of length $N$: $A=(A_1,A_2,\\ldots,A_N)$. Find the number of triples of positive integers $(i,j,k)$ that satisfy all of the following conditions: *   $1\\l","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc318_e"},"statements":[{"statement_type":"Markdown","content":"You are given a sequence of positive integers of length $N$: $A=(A_1,A_2,\\ldots,A_N)$. Find the number of triples of positive integers $(i,j,k)$ that satisfy all of the following conditions:\n\n*   $1\\leq i < j < k\\leq N$,\n*   $A_i = A_k$,\n*   $A_i \\neq A_j$.\n\n## Constraints\n\n*   $3\\leq N\\leq 3\\times 10^5$\n*   $1\\leq A_i \\leq N$\n*   All input values are integers.\n\n## Input\n\nThe input is given from Standard Input in the following format:\n\n$N$ \n$A_1$ $A_2$ $\\ldots$ $A_N$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc318_e","tags":[],"sample_group":[["5\n1 2 1 3 2","3\n\nThe following three triples of positive integers $(i,j,k)$ satisfy the conditions:\n\n*   $(i,j,k)=(1,2,3)$\n*   $(i,j,k)=(2,3,5)$\n*   $(i,j,k)=(2,4,5)$"],["7\n1 2 3 4 5 6 7","0\n\nThere may be no triples of positive integers $(i,j,k)$ that satisfy the conditions."],["13\n9 7 11 7 3 8 1 13 11 11 11 6 13","20"]],"created_at":"2026-03-03 11:01:14"}}