{"problem":{"name":"Trained?","description":{"content":"Takahashi wants to gain muscle, and decides to work out at AtCoder Gym. The exercise machine at the gym has $N$ buttons, and exactly one of the buttons is lighten up. These buttons are numbered $1$ th","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc065_b"},"statements":[{"statement_type":"Markdown","content":"Takahashi wants to gain muscle, and decides to work out at AtCoder Gym.\nThe exercise machine at the gym has $N$ buttons, and exactly one of the buttons is lighten up. These buttons are numbered $1$ through $N$. When Button $i$ is lighten up and you press it, the light is turned off, and then Button $a_i$ will be lighten up. It is possible that $i=a_i$. When Button $i$ is not lighten up, nothing will happen by pressing it.\nInitially, Button $1$ is lighten up. Takahashi wants to quit pressing buttons when Button $2$ is lighten up.\nDetermine whether this is possible. If the answer is positive, find the minimum number of times he needs to press buttons.\n\n## Constraints\n\n*   $2 ≤ N ≤ 10^5$\n*   $1 ≤ a_i ≤ N$\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$N$\n$a_1$\n$a_2$\n:\n$a_N$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc065_b","tags":[],"sample_group":[["3\n3\n1\n2","2\n\nPress Button $1$, then Button $3$."],["4\n3\n4\n1\n2","\\-1\n\nPressing Button $1$ lightens up Button $3$, and vice versa, so Button $2$ will never be lighten up."],["5\n3\n3\n4\n2\n4","3"]],"created_at":"2026-03-03 11:01:14"}}