word = input("Enter a string: ")
length = len(word)

is_f_found = False

# find the first f
for i in range(length):
  if word[i] == "f":
    print(i)  # the first f is found, print its location
    is_f_found = True
    break


# find the last f
for j in range(length-1, i, -1):
  if word[j] == "f":
    print(j)  # the first f is found, print its location
    is_f_found = True
    break

if not(is_f_found):
  print(-1)