#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

S = read().rstrip()
T = list(S)


def test(L, R):
    assert (R - L) % 2 == 0
    if L == R and R == len(S) - 1:
        return False
    remove = []
    remove += T[:L]
    remove += T[R + 1:]
    remove += T[L + 1:R:2]
    se = set(remove)
    return all(x not in se for x in T[L: R + 1:2])


L = len(S)
for i in range(L):
    for j in range(i, L, 2):
        if test(i, j):
            print('Yes')
            exit()
print('NO')