'commit'

TangDou/LuoGuBook/L4_12_2.cpp

@@ -0,0 +1,12 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const double eps = 1e-6;
+int main() {
+    int n;
+    double s = 0;
+    cin >> n;
+    for (double i = 0.1; n - i > eps; i += 0.1) s += i;
+    cout << s;
+    return 0;
+}