## Problem A. How many iterations? ≡

 Author: I. Tuphanov Input file: input.txt Time limit: 1 sec Output file: output.txt Memory limit: 256 Mb

### Statement

Young programmer Vasya is learning the beginnings of the algorithm complexity theory. For starters, he wants to be able to quickly estimate the number of iterations of nested loops. As a first example, he wrote the following code:

 C Pascal long long f(int n) { long long ans = 0; for (int i = 1; i <= n; i++) for (int j = i+1; j <= n; j++) for (int k = j+1; k <= n; k++) ans++; return ans; }  function f(n: integer): int64; var i, j, k: integer; begin result := 0; for i := 1 to n do for j := i+1 to n do for k := j+1 to n do inc(result); end; 

Using your knowledge of the subject, help Vasya calculate f(n) for given n.

### Input file format

Input file contains an integer n.

### Output file format

Output file must contain a single integer — f(n).

1 ≤ n ≤ 106

### Sample tests

No. Input file (input.txt) Output file (output.txt)
1
1

0
2
1000
166167000


## Problem B. Matrix detour: Spiral ≡

 Author: A. Klenin Input file: input.txt Time limit: 2 sec Output file: output.txt Memory limit: 200 Mb

### Statement

Your program must fill the N by N square matrix with integers from 1 to N2; in the following way:
• 1 must be in the top left corner;
• increasing seqeunce of numbers must form a spiral, twisted clockwise and inside.

### Input file format

Input file contains an integer N.

### Output file format

Output file must contain the filled matrix as N lines consisting of N integers each.

1 <= N <= 100

### Sample tests

No. Input file (input.txt) Output file (output.txt)
1
2
1 2
4 3
2
3
1 2 3
8 9 4
7 6 5

0.030s 0.006s 9