n, m, p, q = map(int, input().split())

l = [m for i in range(12)]

for i in range(p, p+q):
    l[i-1] += m
l = l * (10**6 // 12)


c = 1
for i in l:
    n -= i
    if n <= 0:
        print(c)
        break
    c += 1