Question 20
In the given diagram, each vertex of the hexagon $PQRSTU$ is labeled with 0 or 1. Starting counterclockwise from a vertex, he multiplies the labels by 3, 7, 15, 31, 63 and 127 respectively and add the six products. If the starting point is $P$, the final sum is $1\times3+1\times7+0\times15+1\times31+0\times63+1\times127=168$. What is the starting point if the final sum is 180?
