MOD = 10 ** 9 + 7
INF = 10 ** 10
import sys
sys.setrecursionlimit(100000000)
dy = (-1,0,1,0)
dx = (0,1,0,-1)

def main():
    n,m,p,q = map(int,input().split())
    q += p - 1
    cnt = 0
    while n > 0:
        for i in range(1,13):
            cnt += 1
            if p <= i <= q:
                n -= 2*m
            else:
                n -= m
            if n <= 0:
                break
    print(cnt)
if __name__ == '__main__':
    main()