using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using static System.Math;

namespace CSharpSpiral {
	class Program {
		static void Main(string[] args) {
			var sw = new StreamWriter(Console.OpenStandardOutput()) {
				AutoFlush=
#if DEBUG
			true
#else
			false
#endif
			};
			Console.SetOut(sw);
			new Program().Solve(new ConsoleInput(
#if DEBUG
			new StreamReader("../../../inputData.txt")
#else
			Console.In
#endif
			, ' '));
			Console.Out.Flush();
		}
		public void Solve(ConsoleInput cin) {
			var F = new ResidueField((int)Round(Pow(10, 9))+7);
			var N = cin.ReadInt;
			var K = cin.ReadInt;
			var mins = new long[N+2];
			var maxs = new long[N+2];
			var count = new long[N+2];
			for(int i = 1; i<=N+1; i++) {
				mins[i]=F.Add(mins[i-1], i-1);
				maxs[i]=F.Add(maxs[i-1], N+1-i);
				count[i]=F.Sub(maxs[i], mins[i])+1;
			}
			var Res = F.mod(count.Skip(K).Sum());
			Console.WriteLine(Res);
		}

	}
	static class ExtendClass {
		public static void Swap<T>(this T[] A, int x, int y) {
			var tmp = A[x];
			A[x]=A[y];
			A[y]=tmp;
		}
		public static string Join<T>(this IEnumerable<T> X, string separator = " ") => string.Join(separator, X);
		public static IEnumerable<int> Indices<T>(this T[] X) => Enumerable.Range(0, X.Length);
		public static IEnumerable<int> Indices<T>(this T[,] X, int dim)
			=> Enumerable.Range(0, X.GetLength(dim));
		public static string Join<T>(this T[,] X, string separatorD2 = ",", string separatorD1 = "\n")
			=> X.Indices(0).Select(
				i => X.Indices(1).Select(j => X[i, j]).Join(separatorD2)
			).Join(separatorD1);
	}
	class ConsoleInput {
		private readonly TextReader _stream;
		private readonly char _separator = ' ';
		private readonly Queue<string> inputStream;
		public ConsoleInput(TextReader stream, char separator = ' ') {
			this._separator=separator;
			this._stream=stream;
			inputStream=new Queue<string>();
		}
		public string Read {
			get {
				if(inputStream.Count!=0) return inputStream.Dequeue();
				string[] tmp = _stream.ReadLine().Split(_separator);
				for(int i = 0; i<tmp.Length; ++i)
					inputStream.Enqueue(tmp[i]);
				return inputStream.Dequeue();
			}
		}
		public string ReadLine { get { return _stream.ReadLine(); } }
		public int ReadInt { get { return int.Parse(Read); } }
		public long ReadLong { get { return long.Parse(Read); } }
		public double ReadDouble { get { return double.Parse(Read); } }
		public string[] ReadStrArray(long N) {
			var ret = new string[N];
			for(long i = 0; i<N; ++i)
				ret[i]=Read;
			return ret;
		}
		public int[] ReadIntArray(long N) { var ret = new int[N]; for(long i = 0; i<N; ++i) ret[i]=ReadInt; return ret; }
		public long[] ReadLongArray(long N) { var ret = new long[N]; for(long i = 0; i<N; ++i) ret[i]=ReadLong; return ret; }
		public double[] ReadDoubleArray(long N) { var ret = new double[N]; for(long i = 0; i<N; ++i) ret[i]=ReadDouble; return ret; }
		public bool isEOF {
			get { return _stream.Peek()==-1; }
		}
	}
	class ResidueField {
		public readonly long modulo;
		public ResidueField(int mModulo) {
			modulo=mModulo;
		}
		private long[] factorialTable = { 1 };
		private int factorialTableLastIndex { get { return factorialTable.Length-1; } }
		public long mod(long x) => x<0 ? x%modulo+modulo : x%modulo;
		public long Add(long a, long b) => mod(a+b);
		public long Sub(long a, long b) => mod(a-b);
		public long Mul(long a, long b) => mod(a*b);
		public long Pow(long a, long n) {
			if(n==0) return 1;
			var R = 1L;
			n=n<0 ? n%(modulo-1)+(modulo-1) : n%(modulo-1);
			for(; n>0; a=Mul(a, a), n>>=1) {
				if((n&1)!=0) R=Mul(R, a);
			}
			return R;
		}
		private static long extgcd(long a, long b, ref long x, ref long y) {
			if(b==0) {
				x=1; y=0; return a;
			}
			var q = a/b;
			var g = extgcd(b, a-q*b, ref x, ref y);
			var z = x-q*y;
			x=y; y=z;
			return g;
		}
		public long Inv(long a) {
			if(a==0) throw new DivideByZeroException();
			long x = 0, y = 0;
			extgcd(a, modulo, ref x, ref y);
			return mod(x);
		}
		public long Div(long a, long b) => Mul(a, Inv(b));
		public void ExpandFactorialTable(int N) {
			var k = factorialTableLastIndex;
			Array.Resize(ref factorialTable, N+1);
			for(int i = k+1; i<=N; i++) {
				if(i==0) { factorialTable[i]=1; continue; }
				factorialTable[i]=Mul(factorialTable[i-1], i);
			}
		}
		public long Factorial(int n) {
			if(n>factorialTableLastIndex)
				ExpandFactorialTable(n);
			return factorialTable[n];
		}
		public long Permutation(int n, int k) {
			if(k<0||k>n) return 0;
			return Div(Factorial(n), Factorial(n-k));
		}
		public long Combination(int n, int k) {
			if(k<0||k>n) return 0;
			return Div(Factorial(n), Mul(Factorial(k), Factorial(n-k)));
		}

	}
}


Measured memory_bytes: 33620