问题 H: 近似计算

H.cpp

@@ -0,0 +1,18 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+
+int main() {
+    int n;
+    while (cin >> n) {
+        double s = 0;
+        for (int i = 1; i <= n; i += 2) {
+            if (i % 4 == 1)
+                s += 1.0 / i;
+            else
+                s -= 1.0 / i;
+        }
+        cout << fixed << 4 * s << endl;
+    }
+    return 0;
+}