with open('3bigbodyguards.txt') as f:
    string = f.read()
    lines = string.split('\n')
    answer = []


    line_index = 0
    for l in lines:
        char_index = 0
        end_of_line = len(l) - 1
        buddyCount = 0
        for c in l:
            buddyCount = 0
            #skip if its uppercase
            if c.istitle():
                pass
            #check for buddies
            else:
                #if he isn't first in line, check neighbor to left:
                if char_index > 2:
                    if l[char_index -1].istitle() and l[char_index -2].istitle() and l[char_index -3].istitle() :
                        if char_index > 3:
                            if not l[char_index -4].istitle() :
                                buddyCount += 1
                        elif char_index == 3:
                            buddyCount +=1

                #if he isn't the last in line, check neighbor to right:
                if(char_index < end_of_line - 2):
                    if l[char_index +1].istitle() and l[char_index +2].istitle() and l[char_index +3].istitle():
                        if char_index < len(l) - 4:
                            if not l[char_index +4].istitle() :
                                buddyCount += 1
                        elif char_index == len(l) - 3:
                            buddyCount +=1

                if(buddyCount == 2):
                    answer.append(c)
            char_index += 1
        line_index += 1


answerstring = ''
for x in answer:
    answerstring += x
print(answerstring)