diff --git a/.classpath b/.classpath
new file mode 100644
index 0000000..df66b20
--- /dev/null
+++ b/.classpath
@@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" output="target/classes" path="src/main/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="optional" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
+			<attribute name="optional" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" path="target/generated-sources/annotations">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="ignore_optional_problems" value="true"/>
+			<attribute name="m2e-apt" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="target/generated-test-sources/test-annotations">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="ignore_optional_problems" value="true"/>
+			<attribute name="m2e-apt" value="true"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="output" path="target/classes"/>
+</classpath>
diff --git a/.project b/.project
new file mode 100644
index 0000000..acf12e0
--- /dev/null
+++ b/.project
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>ege</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.m2e.core.maven2Builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+		<nature>org.eclipse.m2e.core.maven2Nature</nature>
+	</natures>
+	<filteredResources>
+		<filter>
+			<id>1773398614012</id>
+			<name></name>
+			<type>30</type>
+			<matcher>
+				<id>org.eclipse.core.resources.regexFilterMatcher</id>
+				<arguments>node_modules|\.git|__CREATED_BY_JAVA_LANGUAGE_SERVER__</arguments>
+			</matcher>
+		</filter>
+	</filteredResources>
+</projectDescription>
diff --git a/.settings/org.eclipse.jdt.apt.core.prefs b/.settings/org.eclipse.jdt.apt.core.prefs
new file mode 100644
index 0000000..d4313d4
--- /dev/null
+++ b/.settings/org.eclipse.jdt.apt.core.prefs
@@ -0,0 +1,2 @@
+eclipse.preferences.version=1
+org.eclipse.jdt.apt.aptEnabled=false
diff --git a/.settings/org.eclipse.jdt.core.prefs b/.settings/org.eclipse.jdt.core.prefs
new file mode 100644
index 0000000..c9d1e55
--- /dev/null
+++ b/.settings/org.eclipse.jdt.core.prefs
@@ -0,0 +1,9 @@
+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=17
+org.eclipse.jdt.core.compiler.compliance=17
+org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
+org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
+org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=ignore
+org.eclipse.jdt.core.compiler.processAnnotations=disabled
+org.eclipse.jdt.core.compiler.release=disabled
+org.eclipse.jdt.core.compiler.source=17
diff --git a/.settings/org.eclipse.m2e.core.prefs b/.settings/org.eclipse.m2e.core.prefs
new file mode 100644
index 0000000..f897a7f
--- /dev/null
+++ b/.settings/org.eclipse.m2e.core.prefs
@@ -0,0 +1,4 @@
+activeProfiles=
+eclipse.preferences.version=1
+resolveWorkspaceProjects=true
+version=1
diff --git a/src/main/java/problem13/Example1.java b/src/main/java/problem13/Example1.java
new file mode 100644
index 0000000..10d1880
--- /dev/null
+++ b/src/main/java/problem13/Example1.java
@@ -0,0 +1,24 @@
+package problem13;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+public class Example1{
+  public static void main(String[] args) throws UnknownHostException{
+    long ip = ip_to_long(InetAddress.getByName("10.100.202.34")); // enter your ip
+    long mask =ip_to_long(InetAddress.getByName("255.255.240.0")); // enter your mask
+    ip = (ip & mask) + ((mask ^ 0xFFFFFFFFL) + 1) - 2; // result
+    System.out.printf("%d.%d.%d.%d", (ip >> 24) & 0xFF,(ip >> 16) & 0xFF,(ip >> 8) & 0xFF,ip & 0xFF); // output with dots, answer without it.
+  }
+
+  private static long ip_to_long(InetAddress ip){
+    byte[] octets = ip.getAddress();
+    long result = 0;
+    for(byte octet: octets){
+      result <<= 8;
+      result |= (octet & 0xFF);
+    }
+    return result;
+  }
+
+}