import math

d = int(input())
H = []
H.append(int(input()))
H.append(int(input()))
H.append(int(input()))

if (H[1] == max(H) or H[1] == min(H)) and (H[0] != H[1] and H[1] != H[0]):
    print(0)
    exit()

if d == 0:
    print(-1)
    exit()

if H[0] == H[1] == H[2]:
    if H[0] == 0:
        print(-1)
        exit()
    else:
        print(0)
        exit()

if H[0] < H[2]:
    H[0], H[2] = H[2], H[0]

diff = min(H[0] - H[1], H[1] - H[2])

print(int(math.ceil((diff+0.5)/d)))