diff --git a/SuperPrime_HW2.cpp b/SuperPrime_HW2.cpp
index ec1c77f3..17ba5605 100644
--- a/SuperPrime_HW2.cpp
+++ b/SuperPrime_HW2.cpp
@@ -1,5 +1,6 @@
 #include <iostream>
 #include <vector>
+#include <cmath>
 class Nature {
 private:
   int num;