diff --git "a/0224LJH/202510/12 BOJ \352\267\270\353\236\250\355\214\254.md" "b/0224LJH/202510/12 BOJ \352\267\270\353\236\250\355\214\254.md"
new file mode 100644
index 00000000..5c7e84be
--- /dev/null
+++ "b/0224LJH/202510/12 BOJ \352\267\270\353\236\250\355\214\254.md"	
@@ -0,0 +1,76 @@
+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+
+public class Main {
+	
+	static final char START = 'A';
+	static final char FINAL = 'Z';
+	static String input;
+	static long ans;
+    
+    public static void main(String[] args) throws NumberFormatException, IOException {
+    	init();
+    	process();
+    	print();
+    }
+    
+
+    
+    public static void init() throws NumberFormatException, IOException {
+    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    	input = br.readLine();
+	}
+    
+    public static void process() throws IOException { 	
+    	int idx = 0;
+    	int size = input.length();
+    	long cnt = 0;
+    	long serialStart = 0;
+    	
+    	while(idx < size -1 ){
+    		if (input.charAt(idx) == START) {
+    			serialStart++;
+    			idx++;
+    		}
+    		else if (input.charAt(idx) == START + 1 && serialStart != 0) {
+    			boolean isGramPen = false;
+    			char target = 'B';
+    			long serialLast = 1;
+    			
+    			
+    			while(idx < size) {
+    				if (input.charAt(idx) == target) {
+    					if (target == 'Z') serialLast++;
+    					
+    				} else if(target != 'Z' && input.charAt(idx) == target+1) {
+    					target++;
+    					if (target == 'Z') isGramPen = true;
+    				} else {
+    					break;
+    				}
+    				idx++;
+    			}
+    			
+    			if (isGramPen) cnt += serialStart*serialLast;
+    			serialStart = 0;
+    		} else {
+    			idx++;
+    			serialStart = 0;
+    		}
+    		
+    	}
+    	ans = cnt;
+    }
+    
+
+
+
+	public static void print() {
+		System.out.print(ans);
+
+    }
+}
+```