a,b,n=map(int,input().split())
mod=10**9+7

def prod(A,B,k,l,m):# A:k*l,B:l*m
    C=[[None for i in range(m)] for j in range(k)]

    for i in range(k):
        for j in range(m):
            ANS=0
            for pl in range(l):
                ANS=(ANS+A[i][pl]*B[pl][j])%mod

            C[i][j]=ANS

    return C

def plus(A,B,k,l):# a,B:k*l
    C=[[None for i in range(l)] for j in range(k)]

    for i in range(k):
        for j in range(l):
            C[i][j]=(A[i][j]+B[i][j])%mod

    return C

X=[[0,1]]
A=[[0,b],[1,a]]

POWA=[A]

for i in range(60):
    POWA.append(prod(POWA[-1],POWA[-1],2,2,2))


while n:
    X=prod(X,POWA[n.bit_length()-1],1,2,2)
    n-=1<<(n.bit_length()-1)

print(X[0][0])