diff --git a/problem/P3879/P3879.cpp b/problem/P3879/P3879.cpp
index bf70e219..ce40d773 100644
--- a/problem/P3879/P3879.cpp
+++ b/problem/P3879/P3879.cpp
@@ -5,7 +5,7 @@ using namespace std;
 int main() {
     int n, l;
     string s;
-    map<string, set<int>> m;
+    unordered_map<string, set<int> > m;
     cin >> n;
     for (int i = 1; i <= n; i++) {
         cin >> l;