N,M,P,Q=map(int,input().split())
during=[]
month=1
cnt=0
for i in range(Q):
    x=(P+i)%12
    if x==0:
        x=12
    during.append(x)
while(N>0):
    if month in during:
        N-=2*M
    else:
        N-=M
    month+=1
    if month==13:
        month=1
    cnt+=1
print(cnt)