{"status": "success", "data": {"description_md": "If $n$ is a positive integer, the symbol $n!$ (read \"$n$ factorial\") represents the product of the integers from 1 to $n$. For example, $4! = (1)(2)(3)(4)$ or $4! = 24$. The ones (units) digit of the sum $1! + 2! + 3! + 4! + 5! + 6! + 7! + 8! + 9! + 10!$ is\n\n$\\text{(A)}\\ 1\\qquad\\text{(B)}\\ 3\\qquad\\text{(C)}\\ 5\\qquad\\text{(D)}\\ 7\\qquad\\text{(E)}\\ 9$\n\n___\n\n**[Cayley](https://www.cemc.uwaterloo.ca/contests/past_contests.html#pcf), by [CEMC](https://cemc.uwaterloo.ca/), is licensed under the [CC BY-NC 3.0 DEED](https://creativecommons.org/licenses/by-nc/3.0/). They are not affiliated with or endorse TopsOJ in any way.**\n", "description_html": "<p>If <span class=\"katex--inline\">n</span> is a positive integer, the symbol <span class=\"katex--inline\">n!</span> (read \"<span class=\"katex--inline\">n</span> factorial\") represents the product of the integers from 1 to <span class=\"katex--inline\">n</span>. For example, <span class=\"katex--inline\">4! = (1)(2)(3)(4)</span> or <span class=\"katex--inline\">4! = 24</span>. The ones (units) digit of the sum <span class=\"katex--inline\">1! + 2! + 3! + 4! + 5! + 6! + 7! + 8! + 9! + 10!</span> is</p>\n<p><span class=\"katex--inline\">\\text{(A)}\\ 1\\qquad\\text{(B)}\\ 3\\qquad\\text{(C)}\\ 5\\qquad\\text{(D)}\\ 7\\qquad\\text{(E)}\\ 9</span></p>\n<hr>\n<p><strong><a href=\"https://www.cemc.uwaterloo.ca/contests/past_contests.html#pcf\">Cayley</a>, by <a href=\"https://cemc.uwaterloo.ca/\">CEMC</a>, is licensed under the <a href=\"https://creativecommons.org/licenses/by-nc/3.0/\">CC BY-NC 3.0 DEED</a>. They are not affiliated with or endorse TopsOJ in any way.</strong></p>\n", "hints_md": "", "hints_html": "", "editorial_md": "", "editorial_html": "", "flag_hint": "", "point_value": 1, "problem_name": "2015 Cayley Problem 15", "can_next": true, "can_prev": true, "nxt": "/problem/15_cayley_p16", "prev": "/problem/15_cayley_p14"}}