diff --git a/seive.cpp b/seive.cpp
new file mode 100644
index 00000000..3fd4caf6
--- /dev/null
+++ b/seive.cpp
@@ -0,0 +1,32 @@
+// the following implementation
+// stores only halves of odd numbers
+// the algorithm is a faster by some constant factors
+
+#include <bitset>
+#include <iostream>
+using namespace std;
+
+bitset<500001> Primes;
+void SieveOfEratosthenes(int n)
+{
+	Primes[0] = 1;
+	for (int i = 3; i*i <= n; i += 2) {
+		if (Primes[i / 2] == 0) {
+			for (int j = 3 * i; j <= n; j += 2 * i)
+				Primes[j / 2] = 1;
+		}
+	}
+}
+
+int main()
+{
+	int n = 100;
+	SieveOfEratosthenes(n);
+	for (int i = 1; i <= n; i++) {
+		if (i == 2)
+			cout << i << ' ';
+		else if (i % 2 == 1 && Primes[i / 2] == 0)
+			cout << i << ' ';
+	}
+	return 0;
+}