A. Maximum in Table

An n × n table a is defined as follows:

The first row and the first column contain ones, that is: ai, 1 = a1, i = 1 for all i = 1, 2, …, n.
Each of the remaining numbers in the table is equal to the sum of the number above it and the number to the left of it. In other words, the remaining elements are defined by the formula ai, j = ai - 1, j + ai, j - 1.
These conditions define all the values in the table.

You are given a number n. You need to determine the maximum value in the n × n table defined by the rules above.

Input
The only line of input contains a positive integer n (1 ≤ n ≤ 10) — the number of rows and columns of the table.

Output
Print a single line containing a positive integer m — the maximum value in the table.

Examples
inputCopy
1
outputCopy
1
inputCopy
5
outputCopy
70
Note
In the second test the rows of the table look as follows:

{1, 1, 1, 1, 1}, 
{1, 2, 3, 4, 5}, 
{1, 3, 6, 10, 15}, 
{1, 4, 10, 20, 35}, 
{1, 5, 15, 35, 70}.

#include <iostream>
using namespace std;
///手算，在前一个数基础上，只算底部一条边就行
int main()
{
    int n;
    while(cin >> n)
    {
        switch(n)
        {
        case 1 :
            cout << "1" << '\n';
            break;
        case 2 :
            cout << "2" << '\n';
            break;
        case 3 :
            cout << "6" << '\n';
            break;
        case 4 :
            cout << "20" << '\n';
            break;
        case 5 :
            cout << "70" << '\n';
            break;
        case 6 :
            cout << "252" << '\n';
            break;
        case 7 :
            cout << "924" << '\n';
            break;
        case 8 :
            cout << "3432" << '\n';
            break;
        case 9 :
            cout << "12870" << '\n';
            break;
        case 10 :
            cout << "48620" << '\n';
            break;
        }
    }
    return 0;
}