file rename to standards

(cherry picked from commit 412d3ff1a2)

math/primes_up_to_billion.cpp

@@ -0,0 +1,26 @@
+#include <cstring>
+#include <iostream>
+
+char prime[100000000];
+
+void Sieve(int64_t n) {
+    memset(prime, '1', sizeof(prime));  // intitize '1' to every index
+    prime[0] = '0';                     // 0 is not prime
+    prime[1] = '0';                     // 1 is not prime
+    for (int p = 2; p * p <= n; p++) {
+        if (prime[p] == '1') {
+            for (int i = p * p; i <= n; i += p)
+                prime[i] = '0';  // set all multiples of p to false
+        }
+    }
+}
+
+int main() {
+    Sieve(100000000);
+    int64_t n;
+    std::cin >> n;  // 10006187
+    if (prime[n] == '1')
+        std::cout << "YES\n";
+    else
+        std::cout << "NO\n";
+}