From 62b25e4a6b04af4ccc9974eb0a4c127fb07dce2a Mon Sep 17 00:00:00 2001
From: LiiNi-coder <97495437+LiiNi-coder@users.noreply.github.com>
Date: Fri, 2 Jan 2026 23:35:37 +0900
Subject: [PATCH] =?UTF-8?q?[20260102]=20BOJ=20/=20G5=20/=204=EC=99=80=207?=
 =?UTF-8?q?=20/=20=EC=9D=B4=EC=9D=B8=ED=9D=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../202601/02 BOJ 4\354\231\200 7.md"         | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 "LiiNi-coder/202601/02 BOJ 4\354\231\200 7.md"

diff --git "a/LiiNi-coder/202601/02 BOJ 4\354\231\200 7.md" "b/LiiNi-coder/202601/02 BOJ 4\354\231\200 7.md"
new file mode 100644
index 00000000..13f7922d
--- /dev/null
+++ "b/LiiNi-coder/202601/02 BOJ 4\354\231\200 7.md"	
@@ -0,0 +1,35 @@
+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        long K = Long.parseLong(br.readLine());
+
+        long length = 1;
+        long countInGroup = 2;  //길이 1그룹에선 2개(4, 7)
+        while (K > countInGroup) {
+            K -= countInGroup;
+            length++;
+            countInGroup = 1L << length;
+        }
+        long index = K - 1;
+
+        StringBuilder result = new StringBuilder();
+        for (int i = (int) length - 1; i >= 0; i--) {
+            long bit = (index >> i) & 1;
+            if (bit == 0) {
+                result.append('4');
+            } else {
+                result.append('7');
+            }
+        }
+        System.out.println(result.toString());
+        br.close();
+    }
+}
+
+```