{"trustable":true,"sections":[{"title":"","value":{"format":"HTML","content":"\u003cstyle type\u003d\"text/css\"\u003e pre { text-align:left; font-family: \"Courier New\", Courier, monospace; font-size: 16px; white-space: pre; line-height:20px; text-indent: 0px; }\u003c/style\u003e\u003cdiv class\u003d\"pro_desc\"\u003e\n \u003cp\u003e在一个平面内给定n个点,任意三个点不在同一条直线上,用这些点可以构成多少个平行四边形?一个点可以同时属于多个平行四边形。\u003c/p\u003e\n\u003c/div\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cdiv class\u003d\"pro_desc\"\u003e\n \u003cp\u003e多组数据(\u0026lt;\u003d10),处理到EOF。\u003c/p\u003e\n \u003cp\u003e每组数据第一行一个整数n(4\u0026lt;\u003dn\u0026lt;\u003d500)。接下来n行每行两个整数xi,yi(0\u0026lt;\u003dxi,yi\u0026lt;\u003d1e9),表示每个点的坐标。\u003c/p\u003e\n\u003c/div\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cdiv class\u003d\"pro_desc\"\u003e\n \u003cp\u003e每组数据输出一个整数,表示用这些点能构成多少个平行四边形。\u003c/p\u003e\n\u003c/div\u003e"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre\u003e4\r\n0 1\r\n1 0\r\n1 1\r\n2 0\r\n\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre\u003e1\u003c/pre\u003e"}}]}