P2508 [HAOI2008]圆上的整点

https://www.luogu.com.cn/record/88070866

Luogu/P2508/P2508.cpp

@@ -0,0 +1,35 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    long long r, ans = 1;
+
+    cin >> r;
+
+    for (int i = 2; i * i <= r; i++) {
+        if (r % i == 0) {
+            int cnt = 0;
+
+            while (r % i == 0) {
+                r /= i;
+                cnt++;
+            }
+
+            if (i % 4 == 1) ans *= cnt * 2 + 1;
+        }
+    }
+
+    if (r != 1 && r % 4 == 1) {
+        ans *= 3;
+    }
+
+    cout << ans * 4 << endl;
+
+    return 0;
+}