{"raw_statement":[{"iden":"problem statement","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 $f(N)$."},{"iden":"constraints","content":"*   $0 \\leq N \\leq 10^{18}$"},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$"},{"iden":"sample input 1","content":"12"},{"iden":"sample output 1","content":"1\n\n$f(12) = 12 × 10 × 8 × 6 × 4 × 2 = 46080$, which has one trailing zero."},{"iden":"sample input 2","content":"5"},{"iden":"sample output 2","content":"0\n\n$f(5) = 5 × 3 × 1 = 15$, which has no trailing zeros."},{"iden":"sample input 3","content":"1000000000000000000"},{"iden":"sample output 3","content":"124999999999999995"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}