from collections import deque

LEN = 4
dups = deque(maxlen=LEN)

def hasdups():
    for x in dups:
        if dups.count(x) > 1:
            return True
    return False

with open("input.txt", "r") as f:
    line = f.readline().strip()
    for (index, char) in enumerate(line):
        dups.append(char)
        print(char)
        print(dups)
        if len(dups) >= LEN and not hasdups():
            print(index+1)
            break