Imports System
Public Class Program
Public Shared Function remove_the_N_digit(ByVal num As Integer, ByVal N As Integer) As Integer
Dim str As String = Convert.ToString(num)
str = str.Substring(0, N) & str.Substring(N + 1)
Return Integer.Parse(str)
End Function
Public Shared Function isPrime(ByVal n As Integer) As Boolean
If n < 2 OrElse (n Mod 2 = 0 AndAlso n <> 2) Then
Return False
End If
Dim count As Integer = CInt(Math.Floor(Math.Sqrt(n)))
For i As Integer = 3 To count Step 2
If n Mod i = 0 Then
Return False
End If
Next
Return True
End Function
Public Shared Sub Main(ByVal args As String())
Dim n As Integer = 78919
Dim total_digits As Integer = CInt(Math.Log10(n)) + 1
Dim i As Integer = 0
While i < total_digits
Dim tmp As Integer = remove_the_N_digit(n, i)
If isPrime(tmp) Then
Console.Write("yes number = " & tmp)
Exit While
End If
i += 1
End While
End Sub
End Class
' run:
'
' yes number = 7919
'
