{"trustable":true,"sections":[{"title":"","value":{"format":"HTML","content":"\u003cp\u003eYou are given a point set with $n$ points on the 2D-plane, your task is to find the smallest number of points you need to add to the point set, so that all the points in the set are center symmetric.\u003c/p\u003e\n\u003cp\u003eAll the points are center symmetric means that you can find a center point $(X_c,Y_c)$(not necessarily in the point set), so that for every point $(X_i,Y_i)$ in the set, there exists a point $(X_j,Y_j)$ ($i$ can be equal to $j$) in the set satisfying $X_c\u003d(X_i+X_j)/2$ and $Y_c\u003d(Y_i+Y_j)/2$.\u003c/p\u003e\n\u003ch3\u003eInput\u003c/h3\u003e\n\u003cp\u003eThe first line contains an integer $n(1 \\le n \\le 1000)$.\u003c/p\u003e\n\u003cp\u003eThe next $n$ lines contain $n$ pair of integers $(X_i,Y_i)$ $(-10^6 \\le X_i,Y_i \\le 10^6)$ -- the points in the set\u003c/p\u003e\n\u003ch3\u003eOutput\u003c/h3\u003e\n\u003cp\u003eOutput a single integer -- the minimal number of points you need to add.\u003c/p\u003e"}},{"title":"Sample 1","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003e3\n2 0\n-3 1\n0 -2\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e1\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cbr /\u003e\u003cp\u003eFor sample $1$, add point $(5,-3)$ into the set, the center point can be $(1,-1)$ .\u003c/p\u003e"}}]}