#yuki740
import sys

n,m,p,q=map(int,raw_input().split())
a=[]
res=0
for i in xrange(1,p):
 res+=m
 if res>=n:
  print i
  sys.exit()
for i in xrange(p,p+q):
 res+=m*2
 if res>=n:
  print i
  sys.exit()
for i in xrange(p+q,n/m+1):
 res+=m
 if res>=n:
  print i
  sys.exit()
print -1