diff --git a/ArticulationPoints.cpp b/ArticulationPoints.cpp
index c274dd9..07ea13e 100644
--- a/ArticulationPoints.cpp
+++ b/ArticulationPoints.cpp
@@ -1,6 +1,7 @@
 #include <iostream>
 #include <vector>
 #include <algorithm>
+#include <set>
 using namespace std;
 class Graph
 {