Codeforces 268B. Buttons Solution

Solve in C++:

1. ///**********ALLAH IS ALMIGHTY************///
2. ///AH Tonmoy
3. ///Department of CSE
4. ///Islamic University,Bangladesh
5. #include<iostream>
6. using namespace std;
7. int main()
8. {
9. long long n,s=0;
10. cin>>n;
11. for(int i=1; i<n; i++)
12. {
13. s=s+((n-i)*i);
14. }
15. cout<<s+n<<endl;
16. }