output_description: Print the number of possible values of the sum, modulo (10^9+7).
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N K
attempt: N = [int(e) for e in input().split()]
  nums = []
  u = 10**9 + 7
  t = 0
  s = 0
  Min = 0
  Max = 0
  for i in range(0, N[1]):
      Min += i
      t = i + 1
      Max += N[0] - i
      s = N[0] - i - 1
  ans = Max - Min + 1
  for k in range(N[1] + 1, N[0] + 2):
      Min += t
      t += 1
      Max += s
      s -= 1
      ans += Max - Min + 1
  print(ans % u)
  
problem_description: Statement
  
  We have N+1 integers: 10^{100}, 10^{100}+1, ..., 10^{100}+N.
  
  We will choose K or more of these integers. Find the number of possible values
  of the sum of the chosen numbers, modulo (10^9+7).
samples: [{"input": "3 2", "output": "10\n    \n\nThe sum can take 10 values, as follows:\n\n  * (10^{100})+(10^{100}+1)=2\\times 10^{100}+1\n  * (10^{100})+(10^{100}+2)=2\\times 10^{100}+2\n  * (10^{100})+(10^{100}+3)=(10^{100}+1)+(10^{100}+2)=2\\times 10^{100}+3\n  * (10^{100}+1)+(10^{100}+3)=2\\times 10^{100}+4\n  * (10^{100}+2)+(10^{100}+3)=2\\times 10^{100}+5\n  * (10^{100})+(10^{100}+1)+(10^{100}+2)=3\\times 10^{100}+3\n  * (10^{100})+(10^{100}+1)+(10^{100}+3)=3\\times 10^{100}+4\n  * (10^{100})+(10^{100}+2)+(10^{100}+3)=3\\times 10^{100}+5\n  * (10^{100}+1)+(10^{100}+2)+(10^{100}+3)=3\\times 10^{100}+6\n  * (10^{100})+(10^{100}+1)+(10^{100}+2)+(10^{100}+3)=4\\times 10^{100}+6\n\n* * *"}, {"input": "200000 200001", "output": "1\n    \n\nWe must choose all of the integers, so the sum can take just 1 value.\n\n* * *"}, {"input": "141421 35623", "output": "220280457"}]