diff --git a/release-book.sh b/release-book.sh
index d2bd4b6..012ef68 100755
--- a/release-book.sh
+++ b/release-book.sh
@@ -8,34 +8,24 @@ fatal() {
 	exit 1
 }
 
-get_modification_time() {
-    file_path="$1"
-
-    if [ ! -e "$file_path" ]; then
-    	fatal "file not found: $file_path"
-    fi
-
-    mod_time=$(stat -c "%Y" "$file_path")
-    formatted_mod_time=$(date -d "@$mod_time" "+%Y-%m-%d")
-    echo "$formatted_mod_time"
-}
-
 usage() {
-	>&2 echo "usage: $0 <filename> en|ru"
+	>&2 echo "usage: $0 <filename> en|ru <new_version_number>"
 }
 
-[ $# -ne 2 ] && { usage; exit 1; }
+[ $# -ne 3 ] && { usage; exit 1; }
 
 INPUT="$1"
 LANG="$2"
+VERSION="$3"
 
 case $LANG in
     en|ru) : ;;
     *) fatal "invalid language" ;;
 esac
 
+previous_version=$(( VERSION-1 ))
 target_file="$FILES_DIR/4in1-$LANG.pdf"
-old_date="$(get_modification_time "$INPUT")"
+archive_target_file="$ARCHIVE_DIR/4in1-$LANG-update$previous_version.pdf"
 
 [ -d "$ARCHIVE_DIR" ] || {
 	mkdir "$ARCHIVE_DIR"
@@ -43,7 +33,9 @@ old_date="$(get_modification_time "$INPUT")"
 	chgrp www-data "$ARCHIVE_DIR"
 }
 
+[ -e "$archive_target_file" ] && fatal "invalid version: file \"$archive_target_file\" already exists"
+
 exiftool -author=idb "$INPUT"
 
-mv "$target_file" "$ARCHIVE_DIR/4in1-$LANG-$old_date.pdf"
+mv "$target_file" "$archive_target_file"
 mv "$INPUT" "$target_file"