#yuki740

n,m,p,q=map(int,raw_input().split())
a=[]
for i in xrange(1,13):
 if p<=i and i<=p+q-1:
  a.append(m*2)
 else:
  a.append(m)

x=0
while n>0:
 n-=a[x%12]
 x+=1
print x