n,m,p,q=map(int,input().split())
month=1;check=0;ans=0
while n>0:
    ans+=1
    if month==p:
        check=q
    if check:
        n-=m*2
        check-=1
    else:
        n-=m
    if n<=0: break
    month+=1
    if month>12:
        month=1
print(ans)