#667. [CQOI2007]余数之和

https://sjzezoj.com/submission/64189

S2OJ/667/667.cpp

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+#include <iostream>
+#include <cmath>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+long long n, k, ans;
+
+int main() {
+    cin >> n >> k;
+    ans = n * k;
+    for (int x = 1, gx; x <= n; x = gx + 1) {
+        gx = k / x ? std::min(k / (k / x), n) : n;
+        ans -= (k / x) * (x + gx) * (gx - x + 1) / 2;
+    }
+    cout << ans << endl;
+    return 0;
+}