http://acm.hdu.edu.cn/showproblem.php?pid=1005

#include <iostream>#include <cstring>#include <cstdio>using namespace std;const int N = 2;const int mod = 7;struct Mat{int num[N][N];Mat(){for(int i = 0; i < N; i++)for(int j = 0; j < N; j++)num[i][j] = 0;}};Mat mal(Mat a, Mat b){Mat r;for(int i = 0; i < N; i++)for(int k = 0; k < N; k++)if(a.num[i][k])for(int j = 0; j < N; j++)if(b.num[k][j])r.num[i][j] = (r.num[i][j] + a.num[i][k]* b.num[k][j]) % mod;return r;}Mat mul(Mat a, Mat b, int n){while(n){if(n & 1){n--;b = mal(a, b);}else{n >>= 1;a = mal(a, a);}}return b;}int main(){int a, b, n;while( scanf("%d %d %d", &a, &b, &n) != EOF && a + b + n){if(n <= 2){puts("1");continue;}Mat init, unit, ans;init.num[0][0] = a;init.num[0][1]= b;init.num[1][0] = 1;unit.num[0][0] = 1;unit.num[1][0] = 1;ans = mul(init, unit, n - 2);printf("%d/n", ans.num[0][0]);}return 0;}