codechef Chef and Rainbow Array - 2

Problem Description

Chef loves arrays. But he really loves a specific kind of them - Rainbow Arrays.
The array is a Rainbow Array if it has such a structure:
The first a1 elements equal to 1.
The next a2 elements equal to 2.
The next a3 elements equal to 3.
The next a4 elements equal to 4.
The next a5 elements equal to 5.
The next a6 elements equal to 6.
The next a7 elements equal to 7.
The next a6 elements equal to 6.
The next a5 elements equal to 5.
The next a4 elements equal to 4.
The next a3 elements equal to 3.
The next a2 elements equal to 2.
The next a1 elements equal to 1.
ai is a positive integer, the variables with the same index (a1 in the first statement and a1 in the last one, for example) are equal.
There are no any other elements in array.
For example, {1,1,2,2,2,3,4,5,5,6,7,7,7,6,5,5,4,3,2,2,2,1,1} is a Rainbow Array.
The array {1,2,3,4,5,6,7,6,6,5,4,3,2,1} is not a Rainbow Array, because the sizes of the blocks with the element 6 are different.
Please help Chef to count the number of different Rainbow Arrays that contain exactly N elements.

Input

The first line contains a single integer N.

Output

Output the number of different Rainbow Arrays with N elements, modulo 10^9+7.
Constraints
1 ≤ N ≤ 106

Example

Input #1:
10
Output #1:
0

Input #2:
13
Output #2:
1

Input #3:
14
Output #3:
1

Input #4:
15
Output #4:
7

题解

开始打不开中文题面，又看不懂题面，就看了看别人的代码，结果发现根本看不懂。

之后打开了中文题面……好像只是无脑的DP吧。

#include<cstdio>#include<cstring>#include<cstdlib>#include<iostream>#include<cmath>#include<algorithm>#define ll long long#define mod 1000000007using namespace std;int n;ll f[1000002][8];int main(){scanf("%d",&n);n=(n+1)>>1;int i,j;f[0][0]=1;for(i=1;i<=n;i++)for(j=1;j<=min(i,7);j++)   {f[i][j]=(f[i][j]+f[i-1][j-1])%mod;    f[i][j]=(f[i][j]+f[i-1][j])%mod;   }printf("%lld\n",f[n][7]);return 0;}