Envío 7317

Código

from sys import stdin

def prefix(p):
    m = len(p)
    pi = [0 for _ in range(m)]
    j = 0

    for i in range(1, m):
        while j > 0 and p[i] != p[j]:
            j = pi[j - 1]
        if p[i] == p[j]:
            j += 1
        pi[i] = j 
    return pi

def border(l2r, r2l):
    res = 0 
    for s, e in zip(l2r, r2l):
        if s == e:
            res = max(res, s)
    return res

for line in stdin:
    p = list(line[:-1])
    l2r = prefix(p)

    p.reverse()
    r2l = prefix(p)
    r2l.reverse()

    #print(f"s={p}")
    #print(f"l2r={l2r}")
    #print(f"r2l={r2l}")

    print(border(l2r, r2l))