{"problem":{"name":"Who is missing?","description":{"content":"We have $4$ cards with an integer $1$ written on it, $4$ cards with $2$, $\\ldots$, $4$ cards with $N$, for a total of $4N$ cards. Takahashi shuffled these cards, removed one of them, and gave you a pi","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc236_b"},"statements":[{"statement_type":"Markdown","content":"We have $4$ cards with an integer $1$ written on it, $4$ cards with $2$, $\\ldots$, $4$ cards with $N$, for a total of $4N$ cards.\nTakahashi shuffled these cards, removed one of them, and gave you a pile of the remaining $4N-1$ cards. The $i$\\-th card $(1 \\leq i \\leq 4N - 1)$ of the pile has an integer $A_i$ written on it.\nFind the integer written on the card removed by Takahashi.\n\n## Constraints\n\n*   $1 \\leq N \\leq 10^5$\n*   $1 \\leq A_i \\leq N \\, (1 \\leq i \\leq 4N - 1)$\n*   For each $k \\, (1 \\leq k \\leq N)$, there are at most $4$ indices $i$ such that $A_i = k$.\n*   All values in input are integers.\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$N$\n$A_1$ $A_2$ $\\ldots$ $A_{4N - 1}$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc236_b","tags":[],"sample_group":[["3\n1 3 2 3 3 2 2 1 1 1 2","3\n\nTakahashi removed a card with $3$ written on it."],["1\n1 1 1","1"],["4\n3 2 1 1 2 4 4 4 4 3 1 3 2 1 3","2"]],"created_at":"2026-03-03 11:01:14"}}