file = open("4.txt", "r").read()

suspects = []
for idx, letter in enumerate(file):
    try:
        if letter.isupper() and file[(idx+1)].isupper() and file[(idx+2)].isupper() and file[(idx+4)].isupper() and file[(idx+5)].isupper() and file[(idx+6)].isupper() and file[(idx+3)].islower():
                suspect = str(letter)
                for i in range(1,7):
                    suspect += file[(idx + i)]
                suspects.append(suspect)
    except IndexError:
        print("There are 3 errors of that kind...")
prep = ""
for suspect in suspects:
    prep+= suspect[3]

print(prep)