from decimal import *

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

count = 0

current=1

while(N > 0):
    if(current == 13):
        current = 1
    
    if P <= current <= P+Q-1:
        N = N -2*M
        count += 1
        current += 1
    else:
        N = N-M
        count += 1
        current += 1

print(count)