Create Calculate area and perimeter of N-agon(polygon)

/*
 Problem Description
 Calculate area and perimeter of N-agon(polygon)。
 
 (hint: use structure type to save the coordinate of point)
 
 Input
 N (3<=N<=10)
 
 Coordinate of point (-1000000.000<=x,y<=1000000.000)
 
 Output
 the area and perimeter of N-agon(polygon) (third decimal)
 
 Sample Input
 3
 1 1
 2 3
 3 4
 Sample Output
 0.500 7.256

 */