local mod = 1000000007
local function badd(a, b) return (a + b) % mod end
local n, k = io.read("*n", "*n", "*l")
io.read()
local dp1, dp2 = {}, {}
for i = 1, k + 1 do
  dp1[i] = 0
end
dp1[1] = 1
for i = 1, n do
  local src = i % 2 == 1 and dp1 or dp2
  local dst = i % 2 == 1 and dp2 or dp1
  for j = 1, k + 1 do
    dst[j] = 0
  end
  for j = 0, i - 1 do
    for z = 1, k + 1 - j do
      dst[z + j] = badd(dst[z + j], src[z])
    end
  end
end
local tbl = n % 2 == 1 and dp2 or dp1
local ret = 0
for i = 1, k + 1 do
  ret = badd(ret, tbl[i])
end
print(ret)