HIIT remains

from functools import cache

@cache
def hiit(s):
    if s == "":
        return (0, 0, 0, 0)
    last = s[-1]
    h, hi, hii, hiii = hiit(s[:-1])
    if last == "H":
        return (h + 1, hi, hii, hiii)
    elif last == "I":
        return (h, hi + h, hii + hi, hiii)
    elif last == "T":
        return (h, hi, hii, hiii + hii)
    else:
        return (h, hi, hii, hiii)
        

if __name__ == "__main__":
    s = input()
    print(hiit(s)[3])

Test 1

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 1, in <module>
    from fu...

Test 2

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 1, in <module>
    from fu...

Test 3

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 1, in <module>
    from fu...

Test 4

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 1, in <module>
    from fu...