/*vvv>
		zzzzzI
 .---.  zzuzuI                 .vgggg&,.
+++++=  dunkoI  .WbbWo       JMM9^```?TMB`  ..&gNNg,.   gggggggJ,   qgggggggg] (&&&&&&&&[   c+OA&J,   (&&&&&&+J,   .cJeAA&-.  (&&&&&&&&x   .&AA&=-.
+++++=  dunkoI  Xpbpbp      JM#`           (M#^   ?MMp  MM|   +TMN. JMF      ' |yk      ` dVY    7Vk,  Vy     XV  cVf     ?Y!  JM         V$      `
+++++=  OunkoI  Xppppp      dMN           .MM+     .MM  MM|     MM] JMMMMMM+   |@tqkoh)  ,y0      (V$  yyyyyyyV7  VV           JMWyZWr    TWVVVVW&,
++++++  dZZZZ0  Xppppp      ^HMN,    _.db  WMm,   .MMF  MM|   ..MM` JMF      . |yk       .WV&.   .XW'  yy   4yn.  jyn      +.  JM                #S
`++++`  ?ZZZX=  ?WWWW=        -THMMMMH9^    (TMMMMM9!   MMMMMMM""   JMMMMMMMME |UU.        ?TUUUUY=    UU.   (UU-  ^7TUUUV7!   JUUUUUUUU  7TUNKO*/

//Ricty Diminished
#include "bits/stdc++.h"
using namespace std;typedef long long lint;typedef vector<lint> liv;
//#define rep(i,n) for(int i=0;i<n;++i)
#define all(v) v.begin(),v.end()
#define linf 1152921504606846976
#define MAXN 100100
#define md_1e9_7 1000000007
#define md_998244353 998244353

#define pb push_back
#define _vcppunko4(tuple) _getname4 tuple
#define _getname4(_1,_2,_3,_4,name,...) name
#define _getname3(_1,_2,_3,name,...) name
#define _trep2(tuple) _rep2 tuple
#define _trep3(tuple) _rep3 tuple
#define _trep4(tuple) _rep4 tuple
#define _rep1(n) for(lint i=0;i<n;++i)
#define _rep2(i,n) for(lint i=0;i<n;++i)
#define _rep3(i,a,b) for(lint i=a;i<b;++i)
#define _rep4(i,a,b,c) for(lint i=a;i<b;i+=c)
#define _trrep2(tuple) _rrep2 tuple
#define _trrep3(tuple) _rrep3 tuple
#define _trrep4(tuple) _rrep4 tuple
#define _rrep1(n) for(lint i=n-1;i>=0;--i)
#define _rrep2(i,n) for(lint i=n-1;i>=0;--i)
#define _rrep3(i,a,b) for(lint i=b-1;i>=a;--i)
#define _rrep4(i,a,b,c) for(lint i=a+(b-a-1)/c*c;i>=a;i-=c)
template<class T>
istream& operator>>(istream& is,vector<T>& vec);
template<class T,size_t size>
istream& operator>>(istream& is,array<T,size>& vec);
template<class T,class L>
istream& operator>>(istream& is,pair<T,L>& p);
template<class T>
ostream& operator<<(ostream& os,vector<T>& vec);
template<class T,class L>
ostream& operator<<(ostream& os,pair<T,L>& p);
template<class T>
istream& operator>>(istream& is,vector<T>& vec){ for(T& x: vec) is>>x;return is; }
template<class T,class L>
istream& operator>>(istream& is,pair<T,L>& p){ is>>p.first;is>>p.second;return is; }
//template<class T>
//ostream& operator<<(ostream& os,vector<T>& vec){ os<<vec[0];rep(i,1,vec.size())os<<' '<<vec[i];return os; }
//template<class T>
//ostream& operator<<(ostream& os,deque<T>& deq){ os<<deq[0];rep(i,1,deq.size())os<<' '<<deq[i];return os; }
template<class T,class L>
ostream& operator<<(ostream& os,pair<T,L>& p){ os<<p.first<<" "<<p.second;return os; }

inline void in(){}
template <class Head,class... Tail>
inline void in(Head&& head,Tail&&... tail){ cin>>head;in(move(tail)...); }
template <class T>
inline bool out(T t){ cout<<t<<'\n';return 0; }
inline bool out(){ cout<<'\n';return 0; }
template <class Head,class... Tail>
inline bool out(Head head,Tail... tail){ cout<<head<<' ';out(move(tail)...);return 0; }

template<typename T>
vector<T> make_v(size_t a){ return vector<T>(a); }

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
	return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}
template<typename T,typename V>
typename enable_if<is_class<T>::value==0>::type
fill_v(T &t,const V &v){ t=v; }

template<typename T,typename V>
typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t,const V &v){
	for(auto &e:t) fill_v(e,v);
}//http://beet-aizu.hatenablog.com/entry/2018/04/08/145516

#define rep(...) _vcppunko4((__VA_ARGS__,_trep4,_trep3,_trep2,_rep1))((__VA_ARGS__))
#define rrep(...) _vcppunko4((__VA_ARGS__,_trrep4,_trrep3,_trrep2,_rrep1))((__VA_ARGS__))
#define each(v) for(auto &i:v)
#define lin(...) lint __VA_ARGS__;in(__VA_ARGS__)
#define stin(...) string __VA_ARGS__;in(__VA_ARGS__)
#define vin(type,name,size) vector<type> name(size);in(name)
#define fi i.first
#define se i.second
#define YES(c) cout<<((c)?"YES\n":"NO\n"),0
#define Yes(c) cout<<((c)?"Yes\n":"No\n"),0
#define o(p) cout<<p<<endl,0
#define sp(p) cout<<p<<" "
#define deb(p) cerr<<p<<endl,0
#define dd(n) cout<<fixed<<setprecision(n)

#define inf linf

#define md_tmp template<uint_fast64_t md=1000000007>
md_tmp class mint{
	using u64=uint_fast64_t;

public:
	u64 a;

	constexpr mint(const u64 x=0) noexcept: a(x%md){}
	constexpr u64 &value() noexcept{ return a; }
	constexpr const u64 &value() const noexcept{ return a; }
	constexpr mint operator+(const mint rhs) const noexcept{
		return mint(*this)+=rhs;
	}
	constexpr mint operator-(const mint rhs) const noexcept{
		return mint(*this)-=rhs;
	}
	constexpr mint operator*(const mint rhs) const noexcept{
		return mint(*this)*=rhs;
	}
	constexpr mint operator^(const lint rhs) const noexcept{
		return mint(*this)^=rhs;
	}
	constexpr mint operator/(const mint rhs) const noexcept{
		return mint(*this)/=rhs;
	}
	constexpr mint &operator+=(const mint rhs) noexcept{
		a+=rhs.a;
		if(a>=md)a-=md;
		return *this;
	}
	constexpr mint &operator-=(const mint rhs) noexcept{
		if(a<rhs.a)a+=md;
		a-=rhs.a;
		return *this;
	}
	constexpr mint &operator*=(const mint rhs) noexcept{
		a=a*rhs.a%md;
		return *this;
	}
	constexpr mint &operator^=(const lint rhs) noexcept{
		if(!rhs)return *this=1;
		u64 exp=rhs-1;
		mint base=this->a;
		while(exp){
			if(exp&1)*this*=base;
			base*=base;
			exp>>=1;
		}
		return *this;
	}
	constexpr mint &operator/=(const mint rhs) noexcept{
		a=(*this*(rhs^(md-2))).a;
		return *this;
	}
};
md_tmp istream& operator>>(istream& os,mint<md>& m){
	os>>m.a,m.a%=md;
	return os;
}
md_tmp ostream& operator<<(ostream& os,const mint<md>& m){
	return os<<m.a;
}
md_tmp mint<md> ncr(lint n,lint r){
	mint<md>ncr_res=1,ncr_div=1;
	rep(r)ncr_res*=(n-i),ncr_div*=(r-i);
	return ncr_res/ncr_div;
}
mint<> operator""m(unsigned long long n){ return mint<>(n); }
mint<998244353> operator""m9(unsigned long long n){ return mint<998244353>(n); }
mint<1000003> operator""m3(unsigned long long n){ return mint<1000003>(n); }

int main(){
	lint n,l;in(n,l);
	liv a(n);
	lint s=0,m=linf,p=0;
	rep(n){
		a[i]=i+l;
		s+=a[i];
		if(abs(a[i])<m)p=i,m=abs(a[i]);
	}
	o(s-a[p]);

}

//class UnionFind{
//public://par,rank,init,uf,uf,root,same,unite
//	int par[MAXN],rank[MAXN],sum[MAXN];
//	void init(int n){
//		rep(i,n)par[i]=i,rank[i]=0,sum[i]=1;
//	}
//	UnionFind(int n){
//		init(n);
//	}UnionFind(){}
//	int root(int x){
//		return x==par[x]?x:par[x]=root(par[x]);
//	}
//	bool same(int x,int y){
//		return root(x)==root(y);
//	}
//	void unite(int x,int y){
//		x=root(x);
//		y=root(y);
//		if(x==y)return;
//		if(rank[x]<rank[y]){
//			par[x]=y;
//			sum[y]+=sum[x];
//		} else{
//			par[y]=x;
//			sum[x]+=sum[y];
//			if(rank[x]==rank[y])++rank[x];
//		}
//	}
//};
//UnionFind tr;
//
//struct edge{
//	lint from,to,c;
//};
//bool operator<(edge l,edge r){
//	return l.c<r.c;
//}bool operator>(edge l,edge r){
//	return l.c>r.c;
//}
//vector<edge>g[100010];
//int main(){
//	lint n,m;in(n,m);++n;
//	tr.init(n);
//	lint s,t,c;
//	priority_queue<edge,vector<edge>,greater<edge>>q;
//	rep(m){
//		cin>>s>>t>>c;
//		g[s].pb({s,t,c});
//		if(!s)q.push({s,t,c});
//	}
//	lint ans=0;
//	while(q.size()){
//		s=q.top().from,t=q.top().to,c=q.top().c;q.pop();
//		if(!tr.same(0,t)){
//			tr.unite(0,t);
//			ans+=c;
//			for(auto i:g[t]){
//				q.push(i);
//			}
//		}
//	}
//	/*rep(m){
//		if(!tr.same(g[i].to,0)){
//			tr.unite(g[i].to,0);
//			ans+=g[i].c;
//		}
//	}*/
//	if(tr.sum[tr.root(0)]!=n){
//		cout<<tr.sum[tr.root(0)]-1<<" ";
//	}o(ans);
//}

int maain(){
	lint n;in(n);
	map<lint,lint>ma;
	rep(q,n){
		lint a,b;in(a,b);
		lint plf=b,pp;
		map<lint,lint>t;
		for(int i=2;i*i<=b;++i){
			pp=0;
			while(plf%i==0){
				++pp;plf/=i;
			}if(pp){//ここで因数i**ppがわかる
				t[i]=pp;
			}
		}if(plf!=1){//ここで因数plf**1がわかる
			++t[plf];
		}

		if(a==1){
			for(auto i:t){
				ma[fi]+=se;
			}
		} else{
			lint ans=linf;
			for(auto i:t){
				ans=min(ans,ma[fi]/se);
			}
			o(ans);
		}
	}return 0;
}
//sub-EOF


Measured memory_bytes: 256