diff --git a/Appendix D/solutions/10775.cpp b/Appendix D/solutions/10775.cpp
index 6c991660..1c4360bd 100644
--- a/Appendix D/solutions/10775.cpp	
+++ b/Appendix D/solutions/10775.cpp	
@@ -1,11 +1,51 @@
-// Authored by : BaaaaaaaaaaarkingDog
+// Authored by : erick12(BOJ)/Erickk1212(Github)
 // Co-authored by : -
-// http://boj.kr/****************
-#include <bits/stdc++.h>
+// http://boj.kr/80ae0844bf6e44558f48685b94f1dfd1
+#include<bits/stdc++.h>
 using namespace std;
-
-int main(void){
+int parent[100000];
+int find(int x)
+{
+  if (x == parent[x]) return x;
+  return parent[x] = find(parent[x]);
+}
+void dounion(int x, int y)
+{
+  x = find(x);
+  y = find(y);
+  if (x != y) parent[x] = y;
+}
+void unionfindsetup(int x)
+{
+  for (int i = 0; i <= x; i++)
+  {
+    parent[i] = i;
+  }
+}
+int n, m;
+int main()
+{
   ios::sync_with_stdio(0);
   cin.tie(0);
-  
-}
\ No newline at end of file
+  cin >> n >> m;
+  for (int i = 1; i <= n; i++)
+  {
+    parent[i] = i;
+  }
+  int t = 0;
+  int ans = m;
+  for (int i = 0; i < m; i++)
+  {
+    int num;
+    cin >> num;
+    t = find(num);
+    if (t == 0)
+    {
+      ans = i;
+      break;
+    }
+    parent[t] = t - 1;
+  }
+  cout << ans;
+  return 0;
+}