main(n,m,p,q,c,mo){
	scanf("%d%d%d%d",&n,&m,&p,&q);
	q=p+q-1;
	if(q>12)q=12;
	c=0;
	mo=0;
	for(;;){
		if(n<=0)break;
		((mo+1)>=p&&(mo+1)<=q)?n-=(m*2):(n-=m);
		c++;
		mo++;
		mo%=12;
	}
	printf("%d",c);
}