杭電ACM1005 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

#include<stdio.h>
 
int main(void) {
 int A,B,n,i,an_1,an_2,an;
 while(scanf("%d%d%d",&A,&B,&n) == 3 && n) {
an_1 = 1;
an_2 = 1;
for(i = 3; i <= n; ++i) {
 an = (A * an_2 + B * an_1) % 7;
 an_1 = an_2;
 an_2 = an;
}
printf("%d\n",an);
 }
    return 0;
}