prime multiples

CSES - CSES Problem Set/Mathematics/Prime_Multiples.cpp

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+//  Prime Multiples
+
+#include<bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int main() {
+    ll n, k;
+    cin >> n >> k;
+    vector<ll> primes(k);
+    for (auto &e: primes) cin >> e;
+
+    ll ans = 0;
+    for (ll i = 1; i < (1 << k); i++) {
+        ll prime_product = 1;
+        for (ll j = 0; j < k; j++) {
+            if ( i & (1 << j)) {
+                if (prime_product > n / primes[j]) {
+                    prime_product = n + 1;
+                    break;
+                }
+                prime_product *= primes[j];
+            }
+        }
+        if (__builtin_popcount(i) & 1) {
+            ans += n / prime_product;
+        } else {
+            ans -= n / prime_product;
+        }
+    }
+    cout << ans << endl;
+    return 0;
+}