Add #pragma once

Ayaz Salikhov · Ayaz Salikhov · commit 31f230bae176 · 2020-06-28T03:13:30.000+02:00
diff --git a/sieve.h b/sieve.h
@@ -1,3 +1,4 @@
+#pragma once
 #include <vector>
 #include <cstddef>
 
