After trying hard for many years, Little Q has finally received an astronaut license. To celebrate the fact, he intends to buy himself a spaceship and make an interstellar travel.
Little Q knows the position of $n$ planets in space, labeled by $1$ to $n$. To his surprise, these planets are all coplanar. So to simplify, Little Q put these $n$ planets on a plane coordinate system, and calculated the coordinate of each planet $(x_i,y_i)$.
Little Q plans to start his journey at the $1$-th planet, and end at the $n$-th planet. When he is at the $i$-th planet, he can next fly to the $j$-th planet only if $x_i<x_j$, which will cost his spaceship $x_i\times y_j-x_j\times y_i$ units of energy. Note that this cost can be negative, it means the flight will supply his spaceship.
Please write a program to help Little Q find the best route with minimum total cost.