1247 - LL's lock
Time Limit : 1 Second
Memory Limit : 128 MB
- LL got a box unexpectedly, but the box is protected by a password lock. Besides the lock, there are N sticks with various lengths. LL guessed that the password is the number of different triangles composed by three of these N sticks. Please find this password for him.
Note: two triangles are considered different if they are not composed of the same sticks, even if they have the same size and shape.
- There are multiple cases ended with EOF. Every case have two lines .
The first number of each case is one number——N (3 <= N <= 1000).
The following N positive integers li (1 <= li <= 1000000000) are the lengths of N sticks.
- For each case, output one line containing a single integer—the password deduced.
- sample input
3 1 2 4 8 13 15 4 2 6 9 20 13
- sample output