#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 7;
struct matrix {
int a[5][5]={};
int n,m;
};
matrix I(int n) {
matrix ret;
ret.n=n;
ret.m=n;
for(int i=1;i<=n;i++) ret.a[i][i]=1;
return ret;
}
matrix operator * (matrix a, matrix b) {
matrix ret;
ret.n = a.n;
ret.m = b.m;
for(int i=1;i<=ret.n;i++) {
for(int j=1;j<=ret.m;j++) {
for(int k=1;k<=a.m;k++) {
ret.a[i][j] += a.a[i][k] * b.a[k][j];
ret.a[i][j] %= mod;
ret.a[i][j] += mod;
ret.a[i][j] %= mod;
}
}
}
return ret;
}
matrix qpow(matrix p, int q) {
return ((q&1)?p:I(2)) * (q?qpow(p*p,q/2):I(2));
}
signed main() {
matrix T;
T.n=2; T.m=2;
int a,b,n;
cin>>a>>b>>n;
T.a[1][1]=a; T.a[1][2]=b;
T.a[2][1]=1;
T=qpow(T,n-2);
matrix A;
A.n=2; A.m=1;
A.a[1][1]=1; A.a[2][1]=1;
if(n==1) cout<<1<<endl;
else cout<<(T*A).a[1][1];
}