diff --git a/AcWing/720/720.cpp b/AcWing/720/720.cpp
new file mode 100644
index 00000000..84a40f48
--- /dev/null
+++ b/AcWing/720/720.cpp
@@ -0,0 +1,19 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int a, n, ans;
+
+int main() {
+    cin >> a;
+
+    while (cin >> n, n <= 0) {}
+
+    for (int i = 0; i < n; i++) {
+        ans += i + a;
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}