def main():
    N, M, P, Q = map(int, input().split())
    leaf_lost_per_year = M * (12 + Q)
    year = N // leaf_lost_per_year
    rest_leaf = N % leaf_lost_per_year
    month = 0
    if rest_leaf == 0:
        print(year*12)
        return

    for month in range(1, 13):
        rest_leaf -= M
        if month in range(P, P+Q):
            rest_leaf -= M

        if rest_leaf <= 0:
            break
    else:
        raise ValueError

    print(year*12 + month)


if __name__ == "__main__":
    main()