import sys


def longestunique(val):
    has = [False]*255
    start = 0
    end = 0
    best = 0
    while end != len(val):
        c = val[end]
        if has[ord(c)]:
            has[ord(val[start])] = False
            start += 1
        else:
            has[ord(val[end])] = True
            end += 1
        if end - start + 1 > best:
            best = end - start
    return best

print(longestunique(sys.argv[1]))