diff --git a/history/004_seasaw/src/main/java/com/github/drinkjava2/frog/brain/Input.java b/history/004_seasaw/src/main/java/com/github/drinkjava2/frog/brain/Input.java
new file mode 100644
index 0000000..78f16b4
--- /dev/null
+++ b/history/004_seasaw/src/main/java/com/github/drinkjava2/frog/brain/Input.java
@@ -0,0 +1,26 @@
+/*
+ * Copyright 2018 the original author or authors. 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by
+ * applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
+ * OF ANY KIND, either express or implied. See the License for the specific
+ * language governing permissions and limitations under the License.
+ */
+package com.github.drinkjava2.frog.brain;
+
+/**
+ * Input is the sensor of nerve cell
+ * 
+ * @author Yong Zhu
+ * @since 1.0
+ */
+@SuppressWarnings("serial")
+public class Input extends Zone {
+	public Cell cell; // 这个输入触突属于哪个脑细胞
+
+	public Input(Zone z) {
+		super(z);
+	}
+}