B - Number Sequence

   A number sequence is defined as follows:

f(1) = 1, f(2) = 1, f(n) = (A * f(n - 1) + B * f(n - 2)) mod 7.

Given A, B, and n, you are to calculate the value of f(n).

Input The input consists of multiple test cases. Each test case contains 3 integers A, B and n on a single line (1 <= A, B <= 1000, 1 <= n <= 100,000,000). Three zeros signal the end of input and this test case is not to be processed.
Output For each test case, print the value of f(n) on a single line.
Sample Input

1 1 3
1 2 10
0 0 0

Sample Output

2
5

#include<stdio.h>
#include<string.h>
int main()
{
    int a,b,n,i;
    while(1)
    {
        scanf("%d%d%d",&a,&b,&n);
if(a==0&&b==0&&n==0)
break;
int f[1009];
f[1]=1;
f[2]=1;
for(i=3;i<=1008;i++)
{

f[i]=(a*f[i-1]+b*f[i-2])%7;


}
printf("%d\n",f[(n-1)%1008+1]);
}
return 0;

}

48一个周期，所以只要是48的倍数就可以，因为取余数以后是一样的。1008也是48的一个倍数。