Points symmetry
n different poins P_1, P_2, …, P_n are given on the plane with coordinates (x_i, y_i), i = 1, …, n. The transformation S works as follows: for each point X_0 of the plane we build the point X_1, symmetrical to it with respect to P_1, then we build the point X_2, symmetrical to X_{1 }with respect to P_2 and so on until we bulid the point X_n symmetrical to X_n_{-1 }with respect to P_n. If this transformation S has only one point that does not change its coordinates (fixed point), print its coordinates. If there exist more than one fixed point, print 0. If the fixed point does not exist, print -1.
Input
The first line contains the number of points n. Each of the next n lines contain the integer point coorinates (x_i, y_i), i = 1, …, n. The number of points varies from 1 to 1000 inclusive, x and y are integers from 0 to 1000 inclusive.
Output
Print the coordinates of the fixed point (x, y) if it is unique. If there exist more than one fixed point, print 0. If the fixed point does not exist, print -1.