a,b,n = map(int,input().split())
P = 10 ** 9 + 7
import sys
if n <= 1:
    print(n)
    exit()
    
A = [[a,b],[1,0]]
def seki(X,Y):
    l = [[0] * 2 for _ in range(2)]
    for i in range(2):
        for j in range(2):
            for k in range(2):
                l[i][j] =(l[i][j] + X[i][k] * Y[k][j]) % P
    return l
u = n-1
ans = [[1,0],[0,1]]
while u:
    if u & 1:
        ans = seki(ans,A)
    u >>= 1
    A = seki(A,A)
print(ans[0][0])