I need some help with the format of a paper on overleaf.com [duplicate]

I have been using a template for homework assignments in overleaf.com. It is working well, but unfortunately, there are some ugly checkboxes in every problem line. How do I make this go away ?

Here is the code :

\documentclass[10pt]{article}

\usepackage[margin=1in]{geometry}
\usepackage{amsmath,amsthm,amssymb, graphicx, multicol, array}

\newcommand{\N}{\mathbb{N}}
\newcommand{\Z}{\mathbb{Z}}

\newenvironment{problem}[2][Problem]{\begin{trivlist}
\item[\hskip \labelsep {\bfseries #1}\hskip \labelsep {\bfseries #2.}]}       {\end{trivlist}}

\begin{document}

\title{Pigeonhole Principle}
\author{Name}
\maketitle

\begin{problem}{1}
Let $a_1, a_2, \dots a_n$ be a sequence of integers. Prove that there is    always a subsequence $a_i, a_{i+1}, a_{i+2}, \dots a_{i+k}$, such that  $a_i + a_{i+1} + \dots a_{i+k}$ is a multiple of $n$.
\end{problem}

\begin{proof}
Write a solution here
\end{proof}

\begin{problem}{2}
If there are $25$ points, such that among any three of them there are two     who's distance is less than $1$. Prove that there is always a circle of radius    $1$ which contains $13$ points.
\end{problem}

\begin{proof}
Write a solution here
\end{proof}

\end{document}


The problem is at the end of the solution line there is a box, which I want to remove.

• Do you really expect people to be able to tell you which lines should be added or removed in an unknown document using an unknown template to correct an unknown output? Commented Apr 4, 2016 at 13:17
• @UlrikeFischer I'm new to LaTeX and this site. I don't know what to do. Commented Apr 4, 2016 at 13:33
• Show us the code. Mind you, we likely don't need to see all the problems. Make a copy of your file, and remove code as much as you can from it, without removing the problem. (That is a very short description of how you make a minimal working example (MWE).) Then copy that entire code and paste it into your question. Commented Apr 4, 2016 at 13:35
• Then I would suggest that you learn how to ask questions. Spent a few hours to read questions here that got an answer and try to figure out which information was needed. Commented Apr 4, 2016 at 13:42
• @TorbjørnT. I have posted it. Let me know if it helps. Commented Apr 4, 2016 at 14:29