diff --git a/cache.h b/cache.h
index 443db07..2a76a46 100644
--- a/cache.h
+++ b/cache.h
@@ -39,7 +39,6 @@ enum Status {
 };
 
 const int Earth_radius = 6378;
-const double Pi = 3.14159265358979323846264338327950288;
 
 class Position {
 public:
diff --git a/geostat.cpp b/geostat.cpp
index 95fd2a1..7254b3a 100644
--- a/geostat.cpp
+++ b/geostat.cpp
@@ -12,6 +12,7 @@
 #include <algorithm>
 #include <numeric>
 #include <unistd.h>
+#include <cmath>
 
 void show_usage() {
 	std::cout << "Usage: geostat [options]\n";
@@ -449,7 +450,7 @@ int main(int argc, char** argv) {
 			//std::cout << "Distance between " << i->second->name << " and " << std::next(i)->second->name << " is " << cache_distance(*i->second, *std::next(i)->second) << "<br>";
 			tot_dist += cache_distance(*i->second, *std::next(i)->second);
 		}
-		std::cout << "Total distance between caches: <span class=\"value\">" << std::fixed << tot_dist << "</span> km (equivalent to <span class=\"value\">" << tot_dist / (2 * Pi * Earth_radius) << "x</span> trips around Earth)<br>\n";
+		std::cout << "Total distance between caches: <span class=\"value\">" << std::fixed << tot_dist << "</span> km (equivalent to <span class=\"value\">" << tot_dist / (2 * M_PI * Earth_radius) << "x</span> trips around Earth)<br>\n";
 		std::cout << std::resetiosflags(std::cout.flags());
 		if (sorted_fcaches.size() > 1)
 			std::cout << "Average distance between caches: <span class=\"value\">" << tot_dist / (sorted_fcaches.size() - 1) << "</span> km<br>\n";