diff --git a/Appendix C/solutions/11723.cpp b/Appendix C/solutions/11723.cpp
new file mode 100644
index 00000000..e8052d97
--- /dev/null
+++ b/Appendix C/solutions/11723.cpp	
@@ -0,0 +1,42 @@
+// Authored by : BaaaaaaaaaaarkingDog
+// Co-authored by : -
+// http://boj.kr/5d6d3f1b55a04ea2a5bab1e7b9e28684
+#include <bits/stdc++.h>
+using namespace std;
+
+int state;
+
+int main(){
+  ios::sync_with_stdio(0);
+  cin.tie(0);
+
+  int m;
+  cin >> m;
+  while(m--){
+    string com;
+    int x;
+    cin >> com;
+    if(com == "add"){
+      cin >> x;
+      state |= (1 << (x-1));
+    }
+    else if(com == "remove"){
+      cin >> x;
+      state &= (~(1 << (x-1)));
+    }
+    else if(com == "check"){
+      cin >> x;
+      cout << ((state >> (x-1)) & 1) << '\n';
+    }
+    else if(com == "toggle"){
+      cin >> x;
+      state ^= (1 << (x-1));
+    }
+    else if(com == "all"){
+      state = 0xfffff;
+    }
+    else{ // empty
+      state = 0;
+    }
+  }
+}