Like everyone, cows enjoy variety. Their current fancy is new shapes for pastures. The old rectangular shapes are out of favor; new geometries are the favorite. I. M. Hei, the lead cow pasture architect, is in charge of creating a triangular pasture surrounded by nice white fence rails. She is supplied with N (3 <= N <= 40) fence segments (each of integer length Li (1 <= Li <= 40) and must arrange them into a triangular pasture with the largest grazing area. Ms. Hei must use all the rails to create three sides of non-zero length. Help Ms. Hei convince the rest of the herd that plenty of grazing land will be available. Calculate the largest area that may be enclosed with a supplied set of fence segments. INPUT FORMAT: Each testcase: * Line 1: A single integer N * Lines 2..N+1: N lines, each with a single integer representing one fence segment's length. The lengths are not necessarily unique. Input is terminated by end-of-file SAMPLE INPUT: 5 1 1 3 3 4 OUTPUT FORMAT: For each testcase: A single line with the integer that is the truncated integer representation of the largest possible enclosed area multiplied by 100. Output -1 if no triangle of positive area may be constructed. SAMPLE OUTPUT: 692 [which is 100x the area of an equilateral triangle with side length 4]