Finding the maximum of a string

max_string.py

#-*-coding: utf-8-*-

K = 3
STRINGS = ['abacainstitutebac', 'mycabacrchinstituteve', 'acabacinstinstituterue']


def sort(i, outputs=[]):
    string = ""
    k = i
    while len(string) < len(STRINGS[0])-i:
        string += "".join(list(STRINGS[0])[k])
        for n in range(1, K):
            if STRINGS[n].find(string) != -1 and n<K-1:
                if STRINGS[n+1].find(string) != -1:
                    if string not in outputs:
                        outputs.append(string)
        k += 1
    return outputs

for i in range(len(STRINGS[0])):
    found = sort(i)
    i += 1

print max(found, key=len)