#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <string>
#include <set>
#include <algorithm>
#define MAXN 0x7fffffff
using namespace std;
int a,b,c,d,l,m,n,k[2][2]={{0,1},{1,1}};
void qmi(int x)
{
	if (x==1) return;
	bool bo=false;
	if (x%2==1) bo=true;
	x/=2;
	qmi(x);
	d=(k[0][0]*k[0][0]+k[0][1]*k[1][0])%7;
	l=(k[0][0]*k[0][1]+k[0][1]*k[1][1])%7;
	m=(k[1][0]*k[0][0]+k[1][1]*k[1][0])%7;
	n=(k[1][0]*k[0][1]+k[1][1]*k[1][1])%7;
	k[0][0]=d;
	k[0][1]=l;
	k[1][0]=m;
	k[1][1]=n;
	if (bo==true)
	{
		d=k[0][1]%7;
		l=(k[0][0]*a+b*k[0][1])%7;
		m=k[1][1]%7;
		n=(k[1][0]*a+b*k[1][1])%7;
		k[0][0]=d;
		k[0][1]=l;
		k[1][0]=m;
		k[1][1]=n;
	}
}
int main() 
{
    freopen("sequenceb.in", "r", stdin);
    freopen("sequenceb.out", "w", stdout);
    scanf("%d%d%d",&a,&b,&c);
	a%=7;
	b%=7;
	c-=2;
	k[0][1]=b;
	k[1][1]=a;
	qmi(c);
	printf("%d",(k[0][1]+k[1][1])%7);
    fclose(stdin);
	fclose(stdout);
    return 0;
}