using System;
using System.IO;
using System.Text.RegularExpressions;
class Zubari {
static void Main() {
int c = 0;
foreach( string s in Directory.GetFiles( "." ) )
if ( Regex.IsMatch( Path.GetFileName( s ), @"^Data.*\.txt$" ) )
c++;
Console.WriteLine( c + "個" );
}
}