Decrease example cards weight to prevent overflow when used with CD

examples/gen.go

@@ -55,7 +55,7 @@ func main() {
 			fmt.Println(val)
 		}
 
-		_, err = db.Exec("INSERT INTO cards VALUES(?, ?, ?, ?)", i, 1<<(30-i/50), key, val)
+		_, err = db.Exec("INSERT INTO cards VALUES(?, ?, ?, ?)", i, 1<<(20-i/50), key, val)
 		i++
 	}
 }