{"problem":{"name":"Double Factorial","description":{"content":"For an integer $n$ not less than $0$, let us define $f(n)$ as follows: *   $f(n) = 1$ (if $n < 2$) *   $f(n) = n f(n-2)$ (if $n \\geq 2$) Given is an integer $N$. Find the number of trailing zeros in","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc148_e"},"statements":[{"statement_type":"Markdown","content":"For an integer $n$ not less than $0$, let us define $f(n)$ as follows:\n\n*   $f(n) = 1$ (if $n < 2$)\n*   $f(n) = n f(n-2)$ (if $n \\geq 2$)\n\nGiven is an integer $N$. Find the number of trailing zeros in the decimal notation of $f(N)$.\n\n## Constraints\n\n*   $0 \\leq N \\leq 10^{18}$\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$N$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc148_e","tags":[],"sample_group":[["12","1\n\n$f(12) = 12 × 10 × 8 × 6 × 4 × 2 = 46080$, which has one trailing zero."],["5","0\n\n$f(5) = 5 × 3 × 1 = 15$, which has no trailing zeros."],["1000000000000000000","124999999999999995"]],"created_at":"2026-03-03 11:01:14"}}