我就会用穷举法。。然后n=1000显然超时了呀。。。

There Numbers
Submit: 10   Accepted:1
Time Limit: 1000MS  Memory Limit: 65536K
Description
Given a positive integer n.Choose 3 distinguishing numbers a1,a2,a3 from 1 to n(1<=a1,a2,a3<=n),find the number of ways that satisfying the equation (a1+a2+a3)%3=0.

Input
A positive integer n(0 < n < 1000).


Output
The number of ways that satisfying the equation.


Sample Input

3


Sample Output

1


Source

• Re:求助一道题。菜鸟我 (25) lastone 2007-06-04 00:58:44
• Re:求助一道题。菜鸟我 (512) mxmaxi1234 2011-12-24 09:59:46