N,M,P,Q=map(int,input().split())
for i in range(1,int(N/M)+1):
    if i%12==0:
        if P+Q-1==12:
            N-=2*M
        else:
            N-=M
        if N<=0:
            print(i)
            break
    else:
        if P<=i%12<=P+Q-1:
            N-=2*M
        else:
            N-=M
        if N<=0:
            print(i)
            break