import numpy as np
MOD = pow(10,9)+7
a,b = map(int,input().split())
n = int(input())
A = np.array([[2*a, b - a**2], [1, 0]])
#print(A)
MAX = 70
L = [A]
for i in range(MAX):
  A = np.dot(A,A)
  A = np.mod(A, MOD)
  L.append(A)
#print(L)
X = np.array([[1, 0], [0, 1]])
for i in range(MAX):
  if (n-1>>i)&1 == 1:
    X = np.dot(X,L[i])
    X = np.mod(X,MOD)
ans = X[0,0]*2*a + X[0,1]*2
print(ans%MOD)