N,M,P,Q = map(int,input().split())
count = 0

while N > 0:
    for month in range(1,12+1):
        if P <= month <= (P + Q - 1):
            N -= (2 * M)
            count += 1
        else:
            N -= M
            count += 1
        if N <= 0:
            break

print(count)