connect the output of all four sensors with any port in sequence like D0 – D3
check for change in input for this port
find out how many sensors are blocked like for 1 sensor blocked ip is 1000, for two sensors blocked ip is 1100…. (or it can be reversed)
based on this input set a count like for 1000 ip count is 100, for 1100 ip count is 200…
give pulses to motor till count reaches to 0.
thats all