找规律的题

Number SequenceTime Limit: 2000/1000 MS (Java/Others)????Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 41692????Accepted Submission(s): 8995


#include<stdio.h>int main(){ int a,b,n; while(scanf("%d %d %d",&a,&b,&n)!=EOF&&(a+b+n)!=0) { int f1=1,f2=1,f3=1,t,r[8][8]={0},i,flag=0,x; for(i=3;i<=n;i++) { f3=(a*f2+b*f1)%7; r[f1][f2]=i; f1=f2; f2=f3; if(r[f1][f2]&&flag==0) { t=i-r[f1][f2]+1; i=r[f1][f2]-3; n=(n-i)%t+i ; if(n==i) n=t+i; if(n==(i+1)) {f3=f1;break;} if(n==(i+2)) {f3=f2;break;} i+=2; flag=1; } } printf("%d\n",f3); } return 0;}?