diff --git a/src/main/java/_4/_1/Function.java b/src/main/java/_4/_1/Function.java
new file mode 100644
index 0000000..0483344
--- /dev/null
+++ b/src/main/java/_4/_1/Function.java
@@ -0,0 +1,23 @@
+package _4._1;
+
+public abstract class Function {
+
+	protected Function predecessor;
+
+	public Function() {
+		this.predecessor = null;
+	}
+
+	public Function(Function predecessor) {
+		this.predecessor = predecessor;
+	}
+
+	public double calculate(double x) {
+		if(this.predecessor == null) {
+			return this.apply(x);
+		}
+		return this.predecessor.calculate(x);
+	}
+
+	protected abstract double apply(double x);
+}
diff --git a/src/main/java/_4/_1/SineFunction.java b/src/main/java/_4/_1/SineFunction.java
new file mode 100644
index 0000000..c2d6ace
--- /dev/null
+++ b/src/main/java/_4/_1/SineFunction.java
@@ -0,0 +1,16 @@
+package _4._1;
+
+public class SineFunction extends Function {
+	public SineFunction() {
+		super();
+	}
+
+	public SineFunction(Function predecessor) {
+		super(predecessor);
+	}
+
+	@Override
+	public double apply(double x) {
+		return Math.sin(x);
+	}
+}
diff --git a/src/main/java/_4/_1/SquareFunction.java b/src/main/java/_4/_1/SquareFunction.java
new file mode 100644
index 0000000..f07e58b
--- /dev/null
+++ b/src/main/java/_4/_1/SquareFunction.java
@@ -0,0 +1,16 @@
+package _4._1;
+
+public class SquareFunction extends Function {
+	public SquareFunction() {
+		super();
+	}
+
+	public SquareFunction(Function predecessor) {
+		super(predecessor);
+	}
+
+	@Override
+	protected double apply(double x) {
+		return x * x;
+	}
+}