111321 IP-адрес

file = open('input.txt', encoding='utf-8')
line = file.readline()+'.'
file.close()

point = 0
num = ''
res = 'NO'
for s in line:
    if point <= 3:
        if s in '0123456789':
            num += s
        else:
            if num and s == '.' and 0 <= int(num) <= 255:
                point += 1
                num = ''
            else:
                break

if point == 3 and num and 0 <= int(num) <= 255:
    res = 'YES'

print(res)