1 FI$="":INPUT"Source file";FI$:IFFI$=""THENEND
2 CLOSE:ONERRORGOTO12:OPENFI$FORINPUTAS1:ONERRORGOTO0
3 LC=0:SN=0:INPUT"Count screen number";SN:IFSN=0THEN1
4 CLOSE:OPENFI$FORINPUTAS1
5 IFEOF(1)THENPRINT"Not found":GOTO3
6 LINEINPUT#1,LN$
7 IFVAL(LN$)<>SNTHEN5
8 IFEOF(1)THEN11
9 LINEINPUT#1,LN$:IFVAL(LN$)=SN+1THEN11
10 LC=LC+1:GOTO8
11 CLOSE:PRINTLC;"lines":GOTO3
12 BEEP:RESUME1