diff --git a/problems/1181/21300875_1181.cpp b/problems/1181/21300875_1181.cpp
new file mode 100644
index 0000000..45aaaa8
--- /dev/null
+++ b/problems/1181/21300875_1181.cpp
@@ -0,0 +1,32 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+using namespace std;
+
+bool compare(string &s1, string &s2){
+  if(s1.size() == s2.size()) return s1 < s2;
+  else return s1.size() < s2.size();
+}
+
+int main () {
+  vector<string> v;
+
+  int line = 0;
+  cin >> line;
+
+  for(int i=0; i<line; i++){
+    string s = "";
+    cin >> s;
+    v.push_back(s);
+  }
+  sort(v.begin(),v.end(),compare);
+
+  v.erase(unique(v.begin(), v.end()), v.end());
+
+  for(int i=0;i<v.size(); i++){
+    cout << v[i] << endl;
+  }
+
+  return 0;
+}
diff --git a/problems/1967/21300875_1967.cpp b/problems/1967/21300875_1967.cpp
new file mode 100644
index 0000000..a97d38e
--- /dev/null
+++ b/problems/1967/21300875_1967.cpp
@@ -0,0 +1,7 @@
+#include<iostream>
+using namespace std;
+
+int main(){
+	cout << "prob# 1967" << endl;
+	return 0;
+}
diff --git a/problems/2108/21300875_2108.cpp b/problems/2108/21300875_2108.cpp
new file mode 100644
index 0000000..892f1b7
--- /dev/null
+++ b/problems/2108/21300875_2108.cpp
@@ -0,0 +1,70 @@
+#include <iostream>
+#include <vector>
+#include <cmath>
+#include <utility>
+#include <algorithm>
+using namespace std;
+
+// 정렬기준
+bool check(pair <int,int> &n1, pair <int,int> &n2){
+  if (n1.second==n2.second) return n1.first < n2.first;
+  else return n1.second > n2.second;
+}
+
+int main () {
+
+  //라인 수 받기
+  int line = 0;
+  cin >> line;
+
+  vector<int> v;
+  int sum=0; // 산술평균에 쓸 합
+  int num=0;
+
+  for(int i=0; i<line; i++){
+    cin >> num;
+    v.push_back(num);
+    sum += num;
+  }
+  cout << endl;
+
+  //산술평균
+  int avg = 0;
+  avg = round((float)sum/line);
+  cout << avg << endl;
+
+  //중간값 출력
+  sort(v.begin(),v.end());
+  cout << v[line/2] << endl;
+
+  //최빈값 출력
+  vector<pair <int,int> > cnt;
+  for(int i=0; i<v.size(); i++){
+    if(cnt.empty()){
+      cnt.push_back(pair <int,int> (v[i],1));
+      continue;
+    }
+    if(cnt.back().first==v[i]){
+      pair<int,int> st = cnt.back();
+      st.second++;
+      cnt.pop_back();
+      cnt.push_back(st);
+    }
+    else{
+      cnt.push_back(pair <int,int> (v[i],1));
+    }
+  }
+
+  //최빈값순으로 정렬해야함.
+  sort(cnt.begin(), cnt.end(), check);
+  // 최빈값이 같을땐 두번째 작은 값 출력
+  if (cnt[0].second == cnt[1].second)
+    cout << cnt[1].first << endl;
+  else
+    cout << cnt[0].first << endl;
+
+  //범위 출력
+  cout << v.back()-v.front() << endl;
+
+  return 0;
+}
diff --git a/problems/2581/21300875_2581.cpp b/problems/2581/21300875_2581.cpp
new file mode 100644
index 0000000..3234566
--- /dev/null
+++ b/problems/2581/21300875_2581.cpp
@@ -0,0 +1,35 @@
+#include <iostream>
+#include <algorithm>
+
+using namespace std;
+
+bool isprime(int n) {
+  if(n < 2) return false;
+  for(int i=2; i*i<=n; i++){
+    if (n%i == 0)
+      return false;
+  }
+  return true;
+}
+
+int main() {
+  int m = 0, n = 0;
+  cin >> m;
+  cin >> n;
+
+  int sum = 0, min = 10000;
+
+  for (int i = m; i < n+1; i++){
+      if(isprime(i)){
+        sum+=i;
+        if(min>i) min=i;
+      }
+  }
+  if(min==10000) cout << -1 <<endl;
+  else {
+    cout << sum << endl;
+    cout << min << endl;
+  }
+
+  return 0;
+}
diff --git a/problems/4948/21300875_4948.cpp b/problems/4948/21300875_4948.cpp
new file mode 100644
index 0000000..189f5f8
--- /dev/null
+++ b/problems/4948/21300875_4948.cpp
@@ -0,0 +1,33 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+bool isprime(int n) {
+  if(n < 2) return false;
+  for(int i=2; i*i<=n; i++){
+    if (n%i == 0)
+      return false;
+  }
+  return true;
+}
+
+int main() {
+  int N = 0;
+  vector<int> v;
+  while(1){
+    int cnt = 0;
+    cin >> N;
+    if(N==0) break;
+    for(int i=N+1;i<=2*N;i++){
+      if(isprime(i)) cnt++;
+    }
+    v.push_back(cnt);
+  }
+
+  for(int i=0;i<v.size();i++){
+    cout << v[i] << endl;
+  }
+
+  return 0;
+}