#include #define ft first #define sc second #define lb lower_bound #define ub upper_bound #define pb push_back #define pt(sth) cout << sth << "\n" #define chmax(a, b) {if(ab) a=b;} #define moC(a, s, b) (a)=((a)s(b)+MOD)%MOD using namespace std; typedef long long ll; typedef pair P; static const ll INF=1e18; static const ll MAX=1e5+7; static const ll MOD=1e9+7; ll max(ll a, ll b) {return a>b?a:b;} ll min(ll a, ll b) {return a> N >> K; pt(N*(N+1)/2-(N-K)*(N-K+1)/2+1); }