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

fall_per_year = M*12 + Q*M
month = (N // fall_per_year) * 12
remain_leaf = N - (fall_per_year*(N // fall_per_year))

for i in range(1, 13):
    if remain_leaf <= 0:
        break
    if i >= P and i <= P+Q-1:
        remain_leaf -= M*2
    else:
        remain_leaf -= M
    month += 1


print(month)