(0)<-----|----->(0) |
(0)<-----|----->(0) |
(1)<-----|----->(0) |
(2)<-----|----->(0) |
(1)<-----|----->(1) |
(2)<-----|----->(1) |
(4)<-----|----->(0) |
(1)<-----|----->(0) |
(1)<-----|----->(1) |
(1)<-----|----->(1) |