#include <iostream> using namespace std; int xddcc_pomni(int days) { int sum=0; int money=1; int count=1; for (int i=1;i<=days;i++) { sum+=money; count--; if(count==0) { money++; count=money; } } return sum; } int main() { int days; cin>>days; int money=xddcc_pomni(days); cout <<money<<endl; return 0; }