diff --git a/cluster.cpp b/cluster.cpp
index 0a8c3c1..1384949 100644
--- a/cluster.cpp
+++ b/cluster.cpp
@@ -24,6 +24,7 @@
 #include <iostream>
 #include <vector>
 #include <string>
+#include <cstring>
 
 #include <iostream>
 #include <fstream>