auto save

code.cpp

+#include<bits/stc++.h>
+using namespace std;
+
+int main(){
+    int n;
+    cin>>n;
+    int a=0;
+    for(int i=0;i<n;i++){
+        a+=i;
+    }
+    cout<<a<<endl;
+    return 0;
+}
\ No newline at end of file