n,m,p,q = map(int,input().split())
yr_num = (12+q)*m
yr = n // yr_num

n -= yr*yr_num

li = [m]*12
for i in range(q):
    li[p-1+i] += m

for i in range(12):
    if n <= 0:
        print(yr*12+i)
        exit()
    else:
        n -= li[i]