The function calculates the sum of the alphabetical positions of the letters in the input string (ignoring case) and returns that sum as a spelled-out number.

[CODE]:
```python
def input_string_sum(input_str):
    alpha_position_sum = sum([(ord(char.lower()) - 96) for char in input_str if char.isalpha()])
    num_to_word = {0: "zero", 1: "one", 2: "two", 3: "three", 4: "four", 5: "five", 6: "six", 7: "seven", 8: "eight",
                   9: "nine", 10: "ten", 11: "eleven", 12: "twelve", 13: "thirteen", 14: "fourteen", 15: "fifteen",
                   16: "sixteen", 17: "seventeen", 18: "eighteen", 19: "nineteen", 20: "twenty", 21: "twenty-one",
                   22: "twenty-two", 23: "twenty-three", 24: "twenty-four", 25: "twenty-five", 26: "twenty-six"}
    return num_to_word[alpha_position_sum]

input_str = "bicycle"
print(input_string_sum(input_str))
```
