The password for Century4 is the number of files on the desktop.
I googled how to count files in Powershell and found the command Measure-Object.
So I tried
PS C:\users\century3\desktop> dir | measure-object
Count : 123 // This is our flag
Average :
Sum :
Maximum :
Minimum :
Property :
With this information the password for Century 4 should be 123.
123