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

A = []

for i in range(P,P+Q) :
    A.append(i)

ans = 0
c = 0
while N > 0 :
    ans += 1
    
    if c == 12 :
        c = 1
    else :
        c += 1
    
    if c in A :
        N -= 2*M
    else :
        N -= M

print(ans)