a1, a2, n = map(int, input().split())
i = a2 - a1
an = a1 + (n - 1) * i
print(an)

2d23d75cb86fe4f94dd6945b5e09adce0425b98d
<mask token>

<mask token>
print(an)

a1, a2, n = map(int, input().split())
i = a2 - a1
an = a1 + (n - 1) * i
print(an)
