poj2346

dp

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

int f[6][50];

int main()
{
    //freopen("t.txt", "r", stdin);
    memset(f, 0, sizeof(f));
    f[0][0] = 1;
    for (int i = 1; i <= 5; i++)
        for (int j = 0; j <= 9*i; j++)
            for (int k = 0; k <= 9; k++)
            {
                if (k > j)
                    break;
                f[i][j] += f[i - 1][j - k];
            }
    int n;
    scanf("%d", &n);
    n /= 2;
    int ans = 0;
    for (int i = 0; i <= n * 9; i++)
        ans += f[n][i] * f[n][i];
    printf("%d", ans);
    return 0;
}