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