def main():
    try:
        import pypyjit
        pypyjit.set_param('max_unroll_recursion=-1')
    except:
        pass
    try:
        import sys
        sys.setrecursionlimit(10**7)
    except:
        pass
    from math import sqrt,sin,cos,tan,ceil,radians,floor,gcd,exp,log,log10,log2,factorial,fsum
    from heapq import heapify, heappop, heappush
    from bisect import bisect_left, bisect_right
    import copy
    import random
    from collections import deque,Counter,defaultdict
    from itertools import permutations,combinations
    from decimal import Decimal,ROUND_HALF_UP
    #tmp = Decimal(mid).quantize(Decimal('0'), rounding=ROUND_HALF_UP)
    from functools import lru_cache, reduce
    #@lru_cache(maxsize=None)
    from operator import add,sub,mul,xor,and_,or_,itemgetter
    INF = 10**18
    mod1 = 10**9+7
    mod2 = 998244353
    
    #DecimalならPython
    
    def dot(A1,A2,n):
        # n:行列のサイズ
        A = [[0]*n for _ in range(n)]
        for i in range(n):
            for j in range(n):
                for k in range(n):
                    A[i][j] += A1[i][k]%mod1*A2[k][j]%mod1
                    A[i][j] %= mod1
        return A
        
    def pow_mat(A,k,n):
        # A:累乗する行列, k:累乗数, n:行列Aのサイズ
        P = [[0]*n for _ in range(n)]
        for i in range(n):
            P[i][i] = 1
        while k:
            if k&1:
                P = dot(P,A,n)
            A = dot(A,A,n)
            k >>= 1
        return P
    
    a,b,n = map(int, input().split())
    
    A = [[a,b],[1,0]]
    
    ls = pow_mat(A,n-1,2)
    
    print(ls[0][0]%mod1)
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
if __name__ == '__main__':
    main()