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: def check(s, i, c):
      if i >= len(s):
          return c
      if int(s[i : i + 4]) % 2019 == 0:
          c += 1
          return check(s, i + 4, c)
      elif (
          len(str(int(s[i : i + 5]))) == 5
          and int(s[i : i + 5]) % 2019 == 0
          and int(s[i : i + 5]) != int(s[i : i + 4])
      ):
          c += 1
          return check(s, i + 5, c)
      else:
          return c
  
  
  s = input()
  cnt = 0
  li = []
  for i in range(0, len(s) - 3):
      a = int(s[i : i + 4])
      b = int(s[i : i + 5])
      if a % 2019 == 0:
          cnt += 1
          cnt += check(s, i + 4, 0)
      if b % 2019 == 0 and len(str(b)) == 5:
          cnt += 1
          cnt += check(s, i + 5, 0)
  print(cnt)
  
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"}]