HDUACM 1005

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

#include <cstring>
#include <cstdio>
#include <cstdlib>
#include<iostream>
using namespace std;
 
int rec[51];
 
int main()
{
     int a, b, n;
     rec[0] = rec[1] = rec[2] = 1;
     while(cin>>a>>b>>n&&(a!=0||b!=0||n!=0))
     {
         int beg, end, flag = 0;
         for( int i = 3; i <= n && !flag; ++i )
         {
             rec[i] = ( a * rec[i-1] + b * rec[i-2] ) % 7;
             for( int j = 2; j <= i - 1; ++j )
             {
               if( rec[i] == rec[j] && rec[i-1] == rec[j-1] )
               {
                     beg = j, end = i;
                     flag = 1;
                     break;
               }
           }
        }
         if( flag )
         {
             cout<<rec[beg+(n-end)%(end-beg)]<<endl;
         }
         else
             cout<<rec[n]<<endl;
     }
     return 0;
}