cf#257(Div.2) B. Jzzhu and Sequences

B. Jzzhu and Sequences

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard 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).

Sample test(s)

input

2 3
3

output

1

input

0 -1
2

output

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).

題意：給你一個遞推式，f2=f1+f3-->變形爲：f[i]=f[i-1]-f[i-2];輸入f[1]和f[2]；求第n個數的值；如果你想打表的話勸你放棄吧！肯定會超時的，還記得高中的等差序列嗎！對這絕對是一個週期序列！而且週期爲6；

#include<stdio.h>
int main()
{
   __int64 a[10],x,y,n;
    int i;
    scanf("%I64d%I64d",&x,&y);
    a[1]=x;a[2]=y;
    for(i=3;i<=6;i++)
        a[i]=a[i-1]-a[i-2];
    a[0]=a[6];
    scanf("%I64d",&n);
    n=n%6;
    while(1)
    {
        if(a[n]<0)
            a[n]+=1000000007;
        else break;
    }
    printf("%I64d\n",a[n]%1000000007);
    return 0;
}