N, A, B = map(int, input().split())
D = B - 2 * A

if D > 0:
    res = A * (N - 1) - B * N
elif D < 0:
    if N % 2 == 0:
        res = -A * (N - 1)
    else:
        res = -A * (N - 1) - B
else:
    res = -A * (N + 1)

print(res)