diff --git a/src/day4.cpp b/src/day4.cpp
index f152452..9626114 100644
--- a/src/day4.cpp
+++ b/src/day4.cpp
@@ -5,6 +5,7 @@
 #include <string>
 #include <utility>
 #include <vector>
+#include <cmath>
 
 int part1(const std::vector<std::pair<std::vector<int>, std::vector<int>>> &data) {
   int sum = 0;
diff --git a/src/day6.cpp b/src/day6.cpp
index 4580b0e..73954ba 100644
--- a/src/day6.cpp
+++ b/src/day6.cpp
@@ -4,6 +4,7 @@
 #include <iostream>
 #include <string>
 #include <vector>
+#include <cmath>
 
 struct Data {
   std::vector<int> times;