CodeForces Beta Round #24 C. Sequence of points

Sequence of points

M₁.x = 2A₀.x - M₀.x
M₂.x = 2A₁.x - M₁.x = 2A₁.x - 2A₀.x + M₀.x
　　:
M_n.x = 2(A_n-1.x - A_n-2.x + …… + A₀.x) - M₀.x
M_2n.x = 2(A_n-1.x - A_n-2.x + …… + A₀.x) - M_n.x + M₀.x = M₀.x

y座標も同様。

import sys

A = [map(int,x.split()) for x in sys.stdin]
n,j = A[0]
M = A[1]
A = A[2:]

for i in range(j%(2*n)):
    M[0] = 2*A[i%n][0]-M[0]
    M[1] = 2*A[i%n][1]-M[1]

print M[0],M[1]