input: Write a python function to find the sum of the digits in a number N, then transform that sum into a binary string.
  assert solve(1000) == "1"
  assert solve(150) == "110"
  assert solve(147) == "1100"
  assert solve(333) == "1001"
  assert solve(963) == "10010"
output: def solve(N):
      return bin(sum(int(digit) for digit in str(N)))[2:]