input_list = list(map(int,input().split()))
n, m, p, q = input_list

count_month = 0
cur_month = 1
rest_leaf = n

while rest_leaf > 0:
    count_month += 1
    if count_month % 12 == 0:
        cur_month = 12
    else:
        cur_month = count_month % 12
    
    if p <= cur_month and cur_month <= (p + q - 1):
        rest_leaf -= 2 * m
    else:
        rest_leaf -= m
        
print(count_month)