{"problem":{"name":"KAIBUNsyo","description":{"content":"You are given a sequence of $N$ positive integers: $A=(A_1,A_2, \\dots A_N)$. You can do the operation below zero or more times. At least how many operations are needed to make $A$ a palindrome? *   C","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc206_d"},"statements":[{"statement_type":"Markdown","content":"You are given a sequence of $N$ positive integers: $A=(A_1,A_2, \\dots A_N)$. You can do the operation below zero or more times. At least how many operations are needed to make $A$ a palindrome?\n\n*   Choose a pair $(x,y)$ of positive integers, and replace every occurrence of $x$ in $A$ with $y$.\n\nHere, we say $A$ is a palindrome if and only if $A_i=A_{N+1-i}$ holds for every $i$ ($1 \\le i \\le N$).\n\n## Constraints\n\n*   All values in input are integers.\n*   $1 \\le N \\le 2 \\times 10^5$\n*   $1 \\le A_i \\le 2 \\times 10^5$\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$N$\n$A_1$ $A_2$ $\\dots$ $A_N$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc206_d","tags":[],"sample_group":[["8\n1 5 3 2 5 2 3 1","2\n\n*   Initially, we have $A=(1,5,3,2,5,2,3,1)$.\n*   After replacing every occurrence of $3$ in $A$ with $2$, we have $A=(1,5,2,2,5,2,2,1)$.\n*   After replacing every occurrence of $2$ in $A$ with $5$, we have $A=(1,5,5,5,5,5,5,1)$.\n\nIn this way, we can make $A$ a palindrome in two operations, which is the minimum needed."],["7\n1 2 3 4 1 2 3","1"],["1\n200000","0\n\n$A$ may already be a palindrome in the beginning."]],"created_at":"2026-03-03 11:01:13"}}