diff --git a/BOJ/18870.cpp b/BOJ/18870.cpp
new file mode 100644
index 0000000..731c3c9
--- /dev/null
+++ b/BOJ/18870.cpp
@@ -0,0 +1,35 @@
+#include <iostream>
+#include <algorithm>
+#include <vector>
+using namespace std;
+int n;
+vector <pair<int,int>> v;
+vector <int> ans(1000000);
+int main() {
+    ios_base::sync_with_stdio(0);
+    cin.tie(0);
+    cout.tie(0);
+    int N;
+    cin >> N;
+    for(int i = 0 ; i < N ; i++){
+        int x;
+        cin >> x;
+        v.push_back({x,i});
+    }
+    sort(v.begin(),v.end()); //sort
+    int pi = v[0].first;
+    int cnt = 0;
+    ans[v[0].second] = 0;
+    for(int i = 1 ; i < N ; i++){
+        if(pi == v[i].first){
+            ans[v[i].second] = cnt;
+        } else {
+            ans[v[i].second] = ++cnt;
+            pi = v[i].first;
+        }
+    }
+    for(int i = 0 ; i < N ; i++){
+        cout << ans[i] << ' ';
+    }
+    return 0;
+}