leaf_max,drop,start,period = map(int,input().split())
start-=1
period-=1
current_month = 0
current_leaf = leaf_max
while current_leaf > 0:
    d = drop
    cm = current_month % 12
    if start <= cm <= start + period:
        d*=2
    current_leaf-=d
    current_month+=1
print(current_month)