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 -12

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).

题意：给你一个递推式，f2=f1+f3-->变形为：f[i]=f[i-1]-f[i-2];输入f[1]和f[2]；求第n个数的值；如果你想打表的话劝你放弃吧！肯定会超时的，还记得高中的等差序列吗！对这绝对是一个周期序列！而且周期为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
<0)
a
+=1000000007;
else break;
}
printf("%I64d\n",a
%1000000007);
return 0;
}