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