diff --git a/wonjoon/week15/B_2166.java b/wonjoon/week15/B_2166.java
new file mode 100644
index 0000000..6b981c1
--- /dev/null
+++ b/wonjoon/week15/B_2166.java
@@ -0,0 +1,35 @@
+package week15;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+public class B_2166 {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int n = Integer.parseInt(br.readLine());
+        long[][] polygon = new long[n+1][2];
+
+        for (int i = 0; i < n; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            polygon[i][0] = Long.parseLong(st.nextToken());
+            polygon[i][1] = Long.parseLong(st.nextToken());
+        }
+        polygon[n][0] = polygon[0][0];
+        polygon[n][1] = polygon[0][1];
+
+        double size = 0;
+        long a = 0;
+        long b = 0;
+        for (int i = 0; i < n; i++) {
+            a += polygon[i][0]*polygon[i+1][1];
+            b += polygon[i][1]*polygon[i+1][0];
+        }
+
+        size = Math.abs(a-b)/2.0;
+
+        System.out.println(String.format("%.1f", size));
+//        System.out.println(size);
+    }
+}