--- a/rust/integral-geometry/src/lib.rs	Fri Jul 05 21:16:33 2019 +0300
+++ b/rust/integral-geometry/src/lib.rs	Fri Jul 05 21:48:01 2019 +0300
@@ -500,7 +500,7 @@
     }
 
     pub fn edges_count(&self) -> usize {
-        self.vertices.len() - 1
+        self.vertices.len().saturating_sub(1)
     }
 
     pub fn get_edge(&self, index: usize) -> Line {