a,b,n=map(int,input().split())
if n<=1:
  print(n)
  exit()
l=2
M=10**9+7

def seki(a,b):
  c=[[0]*l for i in range(l)]
  for i in range(l):
    for j in range(l):
      for k in range(l):
        c[i][j]+=a[i][k]*b[k][j]
        c[i][j]%=M
  return c

A=[[a,b],[1,0]]
B=[[1,0],[0,1]]
n-=1
for i in range(30):
  if (n>>i)&1:
    B=seki(A,B)
  A=seki(A,A)

print(B[0][0])