程序代码：

#include<stdio.h>
int main()
{
   int A,B;
   long n,i;
   int f(int A,int B,int n);
   while(scanf("%d%d%ld",&A,&B,&n) !=EOF)
    while(A!=0&&B!=0&&n!=0)
     {
       printf("%d\n",f(A,B,n));
       scanf("%d%d%ld",&A,&B,&n);
     }
    return 0;
}

int f(int A,int B,int n)
   {
      int sum;
      if(n==1||n==2)
        sum = 1;
      else
       sum = (A*f(A,B,n-1)+B*f(A,B,n-2))%7;
      return sum;
   }