n,m,p,q=map(int,input().split())
ans=0
b=[]
for i in range(p-1):
    b.append(m)
for i in range(q):
    b.append(m*2)
for i in range(12-p-q+1):
    b.append(m)
i=0
while n>0:
    n-=b[i%12]
    i+=1
print(i)