450B. Jzzhu and Sequences by李博浩 modulo10^9+7

B. Jzzhu and Sequences
time limit per test1 second
memory limit per test256 megabytes
inputstandard input
outputstandard output
Jzzhu has invented a kind of sequences, they meet the following property:

You are given x and y, please calculate fn modulo 1000000007 (109 + 7).

Input
The first line contains two integers x and y (|x|, |y| ≤ 109). The second line contains a single integer n (1 ≤ n ≤ 2·109).

Output
Output a single integer representing fn modulo 1000000007 (109 + 7).

Examples
inputCopy
2 3
3
outputCopy
1
inputCopy
0 -1
2
outputCopy
1000000006
Note
In the first sample, f2 = f1 + f3, 3 = 2 + f3, f3 = 1.

In the second sample, f2 =  - 1;  - 1 modulo (109 + 7) equals (109 + 6).

本题中modulo10^9+7是说数的规律以6位周期，每6位是一样的，所以只需要计算前六位

#include<iostream>
#define mod 1000000007
using namespace std;
int main()
{
	int a[7];
	cin>>a[1]>>a[2];
	int n;cin>>n;
	for(int i=3;i<=6;i++)
	{
		a[i]=a[i-1]-a[i-2];
	}
	a[0]=a[6];
	cout<<(a[n%6]%mod+mod)%mod;
}