def NAND(x, y):
    return (1 - x) | (1 - y)

a = list(map(str, input().split()))
for i in range(1 << 6):
    p = []
    for j in range(6):
        if (i >> j) & 1:
            p.append(1)
        else:
            p.append(0)
    ok = 1
    for i in range(5):
        for j in range(i + 1, 6):
            if a[i] == a[j] and p[i] != p[j]:
                ok = 0
    if ok == 0:
        continue
    if NAND(NAND(NAND(p[0], p[1]), p[2]), NAND(NAND(p[3], p[4]), p[5])):
        if ok:
            print('YES')
            exit()

print('NO')