dic = {chr(i): 0 for i in range(ord('a'), ord('z') + 1)}

s = input()
left = 0; ans = len(s)
for right, ch in enumerate(s):
    dic[ch] += 1
    while all(dic.values()):
        ans = min(ans, right - left + 1)
        dic[s[left]] -= 1
        left += 1
print(ans)