'commit'

TangDou/KaoShi/开关门.cpp

@@ -0,0 +1,18 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 1010;
+int a[N];
+int n, cnt;
+
+int main() {
+    cin >> n;
+    for (int i = 1; i <= n; i++)
+        for (int j = 1; j <= 2 * n; j++)
+            if (j % i == 0)a[j] = !a[j];
+
+    for (int i = 1; i <= 2 * n; ++i)
+        if (a[i]) cnt++;
+    printf("%d", cnt);
+    return 0;
+}