In each question, the first and the last sentences of the passage are numbered S1 and S6 respectively. The rest of the passage is split into four parts. These four sentences are jumbled. Read the sentences and identify their correct and logical order.

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S1: While crossing a busy road we should obey the policeman on duty.
P: We should always cross the road at the zebra crossing.
Q: We must look to the signal lights and cross the road only when the road is clear.
R: If there are no signal lights at the crossing, we should look to the right, then to the left and again to the right before crossing the road.
S: If the road is not clear we should wait.
S6: We should never run while crossing a road.
The Proper sequence should be: