# A*B def mat_mul(A, B, mod): C = [[0]*len(B[0]) for i in range(len(A))] for i in range(len(A)): for k in range(len(B)): for j in range(len(B[0])): C[i][j] = (C[i][j] + A[i][k]*B[k][j])%mod return C #A**n def mat_pow(A, n, mod): B = [[0]*len(A) for i in range(len(A))] for i in range(len(A)): B[i][i] = 1 while n > 0: if n & 1 == 1: B = mat_mul(A, B, mod) A = mat_mul(A, A, mod) n = n>>1 return B # https://yukicoder.me/problems/no/891 a, b, n = map(int, input().split()) X = [0, 1] A = [[a, b], [1, 0]] mod = 10**9+7 A = mat_pow(A, n-1, mod) ans = 0 for i in range(2): ans += A[0][i]*X[1-i] print(ans%mod)