Solution.cs

using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text.RegularExpressions;
using System.Text;
using System;

class Solution {
    static string encryption(string s) {
        var rows = (int)Math.Ceiling(Math.Sqrt(s.Length));

        var lines = new string[rows];
        for(int i = 0; i<s.Length; i++)
            lines[i%rows] += s[i];

        return string.Join(" ", lines);
    }

    static void Main(string[] args) {
        TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);

        string s = Console.ReadLine();

        string result = encryption(s);

        textWriter.WriteLine(result);

        textWriter.Flush();
        textWriter.Close();
    }
}