input: Write a python function to merge two strings by taking the first two characters of the first string and appending the characters from the third position of the second string.
  assert merge_strings("He went to the store", "She visited the store") == "He visited the store"
  assert merge_strings("Good morning", "Wonderful day") == "Goderful day"
  assert merge_strings("12345", "67890") == "12890"
output: def merge_strings(str1, str2):
      return str1[:2] + str2[2:]