# import pypyjit
# pypyjit.set_param('max_unroll_recursion=-1')
from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

def matrix_mul(A,B,mod = None):
    nA = len(A)
    mA = len(A[0])
    mB = len(B[0])
    
    tmp = [[0]*mB for _ in range(nA)]
    
    if mod is None:
        for i in range(nA):
            for j in range(mB):
                tmp[i][j] = sum(A[i][k]*B[k][j] for k in range(mA))
        return tmp
    
    for i in range(nA):
        for j in range(mB):
            tmp[i][j] = sum(A[i][k]*B[k][j]%mod for k in range(mA))%mod
    return tmp
    

def matrix_pow(A,n,mod = None):
    nbit = list(str(bin(n))[2:])
    nbit = [int(i) for i in nbit]
    N = len(A)
    C = [[0]*N for _ in range(N)]
    B = A
    for i in range(N):
        C[i][i] = 1
        
    if mod is None:
        
        for i in range(len(nbit)):
            if nbit[-1-i] == 1:
                C = matrix_mul(C,B)
            
            B = matrix_mul(B,B)
        return C
        
    for i in range(len(nbit)):
        if nbit[-1-i] == 1:
            C = matrix_mul(C,B,mod)
        
        B = matrix_mul(B,B,mod)
    
    return C

a,b,n = map(int,input().split())
mod = 10**9 + 7
if n==0:
    print(0)
    exit()
if n==1:
    print(1)
    exit()
I = [[0],[1],[(a)%mod]]
A = [[0,1,0],[0,0,1],[0,b,a]]
Z = matrix_pow(A,n,mod)
B = matrix_mul(Z,I,mod)
print(B[0][0])