C :

#include<stdio.h>
#include<string.h>
int main()
{
    int a,b,n,i;
    while(1)
    {
        scanf("%d%d%d",&a,&b,&n);
		if(a==0&&b==0&&n==0)
			break;
		int f[1009];
		f[1]=1;
		f[2]=1;
		for(i=3;i<=1008;i++)
		{

			f[i]=(a*f[i-1]+b*f[i-2])%7;


		}
		printf("%d\n",f[(n-1)%1008+1]);
	}
	return 0;
}

C++ :

#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;

long long f[60];

int main()
{
	int a,b,c;
	while(cin>>a>>b>>c)
	{
		if(a==0 && b==0 && c==0)
			break;
		memset(f,0,sizeof(f));
		int start=0,end=0,flag=0;
		f[1]=1;
		f[2]=1;
		for(int i=3;i<=c && flag==0;i++)
		{
			f[i]=(a*f[i-1]+b*f[i-2])%7;
			for(int j=2;j<i;j++)
			{
				if(f[i]==f[j] && f[i-1]==f[j-1])
				{
					start=j;
					end=i;
					flag=1;
					break;
				}
			}
		}
		if(flag==1)
			cout<<f[start+(c-end)%(end-start)]<<endl;
		else
			cout<<f[c]<<endl;
	}
	
}

Java :

import java.util.Scanner;
class deal{
	private final int N=60;
	public int[] ans=new int[N];
	public int[][] flag=new int[10][10];
	public deal(){}
	private void init()
	{
		for(int i=0;i<10;i++)
		{
			for(int j=0;j<10;j++)
			{
				flag[i][j]=-1;
			}
		}
	}
	public void solve(int A,int B,int n){
		ans[0]=ans[1]=1;
		init();
		flag[1][1]=0;
		int pre=1,next=2;
		int i;
		for(i=2;i<n;i++)
		{
			ans[i]=(A*ans[i-1]+B*ans[i-2])%7;
			if(flag[ans[i-1]][ans[i]]!=-1)
			{
				pre=flag[ans[i-1]][ans[i]];
				next=i-1-pre;
				break;
			}
			flag[ans[i-1]][ans[i]]=i-1;
		}
		n--;
		if(n<i)System.out.println(ans[n]);
		else
		{
			System.out.println(ans[pre+(n-pre)%next]);
		}
	}
}
public class Main{
	public static void main(String...strings)
	{
		Scanner in = new Scanner(System.in);
		int A,B,n;
		deal h = new deal();
		while(in.hasNext())
		{
			A=in.nextInt();
			B=in.nextInt();
			n=in.nextInt();
			if(A+B+n==0)break;
			h.solve(A, B, n);
		}
	}
}