diff --git a/Appendix D/solutions/18116.cpp b/Appendix D/solutions/18116.cpp
index 6c991660..3b87220b 100644
--- a/Appendix D/solutions/18116.cpp	
+++ b/Appendix D/solutions/18116.cpp	
@@ -1,11 +1,42 @@
-// Authored by : BaaaaaaaaaaarkingDog
+// Authored by : uhwan0723
 // Co-authored by : -
-// http://boj.kr/****************
+// http://boj.kr/23f94068108e4bdba086c2b011dc5a3a
 #include <bits/stdc++.h>
 using namespace std;
 
+const int mx = 1e6+5;
+int n, a, b, c, par[mx], sz[mx];
+
+int find(int x){
+  if(par[x] < 0) return x;
+  return par[x] = find(par[x]);
+}
+
+void uni(int x, int y){
+  int u = find(x), v = find(y);
+  if(u == v) return;
+  if(-par[u] < -par[v]) swap(u, v);
+  if(par[u] == par[v]) --par[u];
+  par[v] = u;
+  sz[u] += sz[v];
+}
+
 int main(void){
   ios::sync_with_stdio(0);
   cin.tie(0);
-  
-}
\ No newline at end of file
+  cin >> n;
+  fill(par, par+mx, -1);
+  fill(sz, sz+mx, 1);
+  while(n--){
+    char command;
+    cin >> command;
+    if(command == 'I'){
+      cin >> a >> b;
+      uni(a, b);
+    }
+    else{
+      cin >> c;
+      cout << sz[find(c)] << '\n';
+    }
+  }
+}